JP3386299B2 - Wavelength stabilizer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to stabilize the oscillation wavelength of a wavelength multiplexing light source for constructing a wavelength multiplexing network in an optical access system such as long-distance optical fiber communication, optical subscriber communication and optical CATV. The present invention relates to a wavelength stabilization device used in.

[0002]

2. Description of the Related Art The wavelength division multiplexing system has a great advantage that the scale of the network can be flexibly expanded without modifying the installed optical fiber infrastructure. Therefore, a long distance system or an access system is constructed. Above is an important technology. By the way, 2 nm in the 1.5 μm band
When wavelength division multiplex communication of 16 wavelengths is performed at a wavelength interval of, since the oscillation wavelength of a normal distributed feedback semiconductor laser changes by 0.1 nm / ° C with respect to temperature change, if there is a temperature change of 30 ° C. The oscillation wavelength fluctuates by 3 nm. This is a variation in which the wavelength interval exceeds 2 nm, and a wavelength division multiplexing communication system cannot be constructed with such a wavelength variation.

As one method for stabilizing the oscillation wavelength of a semiconductor laser, a method using a diffraction grating spectrometer has been reported (1955, IEICE Communications Society Conference, B-699, September 1995, Miyaji). Masahide, Masanori Kogusu, Shigeru Oshima, "Wavelength Stabilization Method in High-Density Wavelength Multiplexing Transmission"). FIG. 8 shows the configuration of the diffraction grating spectrometer. The wavelength-multiplexed signal lights λ _{1 to} λ ₄ propagating through the optical waveguide 501 at the center of the arrayed waveguide are emitted into the air from the end faces of the waveguide. The outgoing beam 505 is a convex lens 5 with a divergent focal length f.
It is incident on 03. The convex lens 503 is placed at a distance f from the end face of the waveguide 501, and the outgoing beam 505
Becomes a parallel beam 506 and illuminates the diffraction grating 504.
Here, the diffracted light 507 is diffracted according to the wavelength and the diffracted light 507 is reflected by the lens 5.
After passing through 03, it becomes a convergent beam 508 and is converged on the waveguide end face of the arrayed waveguide. Since the convergence point differs depending on the wavelength, signal lights of different wavelengths can be obtained from the waveguides 509 to 512 of the arrayed waveguide. FIG. 9 shows the transmission loss with respect to the wavelength of each waveguide. For example, the waveguide 511
Let us assume that the transmission loss curve of is given in FIG.
The laser light is directly intensity-modulated with a minute sinusoidal current of low frequency f ₀ , the output from the optical waveguide is detected by the light receiving element, and the f ₀ component is synchronously detected. If the wavelength corresponds to the point a of the A curve, the synchronous detection output becomes maximum, and if the wavelength corresponds to the point b, the output is smaller than that. The laser wavelength is controlled so that the coherent detection output becomes maximum. The temperature characteristic of the diffraction grating spectroscope shown in FIG. 8 is 0.0005 nm / ° C., and is ± 0.01 nm even with a temperature change of 50 ° C.

Since the diffraction grating spectroscope of FIG. 8 has excellent temperature characteristics, it can be used as a so-called wavelength standard. As long as the characteristics of FIG. 9 are used, 155
1n as 1nm, 1552nm, 1553nm
Wavelength stabilization can be performed only at discrete wavelength values at m intervals. In practice, the wavelength reference device has a form of use in which many wavelength multiplexing light sources are controlled by one wavelength reference device. The wavelength of the light source is set more finely and variously according to the system requirements. Also, when the wavelength characteristics of wavelength routers and filters placed in network nodes change depending on the environment,
Accordingly, it is necessary to change the wavelength of the light source from the initial set value to the new set value.

One method of controlling the wavelength with a finer wavelength interval in the diffraction grating spectroscope of FIG. 8 is to increase the focal length of the lens 503. Report (The Institute of Electronics, Information and Communication Engineers, IEICE Technical Report OCS95-37, July 1995, Masahiro Kogusu,
According to Masahide Miyaji, Shigeru Oshima, “Highly-stabilized optical multiplexer / demultiplexer”), a reflective blazed diffraction grating with a grating number of 600 / mm is used, and the mode field radius of the waveguide is 5 μm.
By using a lens having a focal length f of 62 mm, the half-value width of the transmission loss of one waveguide shown in FIG. 9 can be set to 0.2 nm (in the case of FIG. 9, f is 25).
The half width at 0.5 mm is 0.5 nm). This means that the wavelength change of 1 nm is about 5 on the end face of the waveguide at the focal point of the lens.
It corresponds to a position change of 0 μm. When a screen is placed at the end face of the waveguide perpendicularly to the optical axis, it is assumed that a convergent beam with a diameter of 10 μm in the mode field is diffracted with an increase in wavelength and moves in the direction of the arrow in FIG. If the converged beam irradiates the area 521 of 10 μm × 10 μm like the spot 527, the wavelength is 1551.0 nm.
Areas 522, 523, 524, 525 and 526 are 155
1.2 nm, 1551.4 nm, 1551.6 nm, 1
It corresponds to wavelengths of 551.8 nm and 1552.0 nm.

[0006]

In order to form the arrayed waveguide structure of FIG. 10, a clad 529 is formed around the core 528 as shown in FIG. 11 and the coupling of light between the waveguides is prevented. Since it is necessary to provide the air layer 530 in the clad between the waveguides, the waveguide pitch of the array waveguide is 2
Only about 0 μm. This means that the reference wavelength can be selected only at wavelengths at 0.4 nm intervals because the array waveguide is used on the output side of the optical multiplexer / demultiplexer. If the focal length of the lens is 122 mm, which is twice 61 mm, and the array waveguide is arranged at a position 122 mm from the lens, the resolution is doubled.
It becomes possible to set reference wavelengths at m intervals. However, the device becomes larger by that amount, and it becomes more susceptible to temperature and mechanical fluctuations, and as a countermeasure, the device becomes larger and the cost rises and handling becomes inconvenient.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to control the oscillation wavelength at a finer wavelength interval, and to improve the characteristics of the multiplexer / demultiplexer of the node. Even if the wavelength characteristic of the transmission line of such a network changes in accordance with changes in environmental conditions, the reference wavelength can be arbitrarily set with the accuracy of the wavelength interval, and a single device can oscillate many semiconductor lasers. An object of the present invention is to provide a compact and economical wavelength stabilizer capable of controlling wavelength.

[0008]

In order to achieve this object, the present invention provides a first to an n-th oscillator having different oscillation wavelengths.
(Where, n is an integer of n ≧ 2) was combined by n and the controlled semiconductor laser, an optical multiplexer each portion of each of the output light of the n-number of the controlled semiconductor laser focus One wave output light
Means for directing the One of the optical waveguide, wherein from the one optical waveguide
A means for radiating the combined output light into the air and irradiating it to a reflection type diffraction grating spectroscope through a convex lens, and a light receiving element array composed of a plurality of light receiving elements by the convex lens for diffracted light from the reflection type diffraction grating spectroscope. A means to converge on top and two switches
With Ji, Ru the neighbors on the light receiving element array two light receiving element
When the two switches are selected by the two switches,
Multiple light reception on the light receiving element array by one switch
Waves formed by a plurality of converging beam spots respectively corresponding to the first to nth semiconductor lasers by sequentially scanning the element
A means for detecting a long-corresponding output, an irradiation position on the light-receiving element array of one convergent beam spot corresponding to one semiconductor laser of the n controlled semiconductor lasers, and an irradiation position of the one convergent beam spot. said amount proportional to the displacement amount between the predetermined reference position on the light receiving element array
Wavelength information by wavelength corresponding output and each predetermined reference wavelength information
Means for detecting as an error signal obtained by comparison with the information, and the oscillation of the one semiconductor laser so that the one converged beam spot is incident on the reference position by returning the error signal to the one semiconductor laser. Means for automatically controlling the wavelength, and n according to the scanning of the output of the light receiving element array.
Means for causing the control to be sequentially repeated for each of the controlled semiconductor lasers, the first to n-th n-th
The oscillation wavelength of each semiconductor laser can be set to a desired value.

Further, the first group has different oscillation wavelengths.
To n-th (where n is an integer of n ≧ 2) n controlled semiconductor lasers of the first group to the m-th group (m = ≧ 2) of controlled semiconductor lasers, and the first group To m optical multiplexers for multiplexing a part of each output light of the controlled semiconductor lasers of the m-th group into one multiplexer for each group to obtain a combined output of each group , The i-th (1
≤ i ≤ m) means for selecting the combined output of the optical multiplexer and guiding it to one optical waveguide, and radiating the combined output light from the one optical waveguide into the air and reflecting it through a convex lens. A means for irradiating the diffraction grating spectroscope, a means for converging the diffracted light from the reflection type diffraction grating spectroscope on the light receiving element array composed of a plurality of light receiving elements by the convex lens, and two switches are used.
The two adjacent photodetectors on the photodetector array.
With the two switches selected, the two switches
Switch is used to connect multiple light receiving elements on the light receiving element array.
Means for detecting the output corresponding to each wavelength by a plurality of converging beam spots respectively corresponding to the first to nth semiconductor lasers by the next scanning, and the n controlled semiconductor lasers of each group . Proportional to the amount of positional deviation between the irradiation position of one convergent beam spot on the light receiving element array corresponding to one of the semiconductor lasers and a predetermined reference position of the one converged beam spot on the light receiving element array. Quantity the wave
Wavelength information based on long-corresponding output and predetermined reference wavelength information
Means for detecting as an error signal obtained by comparing the error signal with the oscillation wavelength of the one semiconductor laser so that the one converged beam spot is incident on the reference position by returning the error signal to the one semiconductor laser. Automatically controlling the output of the light-receiving element array, the means for repeating the control up to the n-th semiconductor laser in accordance with scanning,
Means for repeating the control of the semiconductor lasers of the group m to the group m, and the oscillation wavelengths of the semiconductor lasers of the groups 1 to m can be set to desired values. ing.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The wavelength stabilizing device according to the present invention comprises:
A part of the output light of each of the n semiconductor lasers of the first to n-th (where n is an integer of n ≧ 2) whose different oscillation wavelengths are in the order of small to large or large to small is optically combined. The light is combined with a wave guide and guided to an optical waveguide, and the output light is emitted from the optical waveguide into the air and radiated to a reflective diffraction grating spectroscope through a convex lens, and the diffracted light from the reflective diffraction grating spectroscope is projected onto the convex lens. Converges on a light receiving element array composed of a plurality of light receiving elements, scans the output of the light receiving element array to detect the oscillation wavelength of the first semiconductor laser, and receives the desired oscillation wavelength of the first semiconductor laser. An amount proportional to the amount of positional deviation from the first reference light receiving element is fed back to the first semiconductor laser and
The oscillation wavelength is controlled so that the diffracted light is incident on the reference light-receiving element, the output of the light-receiving element array is scanned, and the same control is sequentially repeated until the nth semiconductor laser.
The reference light receiving element can be set to any light receiving element in the light receiving element array.

Further, in order to control a large number of semiconductor lasers of the first group to the m-th group (m is an integer of m ≧ 2), the p-th group (n-th group consisting of n _p semiconductor lasers having different oscillation wavelengths) p is a semiconductor laser integer) of 1 ≦ p ≦ m, corresponding to each of the part of the output light of the n _p semiconductor laser from the first in a large oscillation wavelength from the small or the large to the small of the order Which are combined by each optical multiplexer and guided to the p-th optical waveguide to form first to m-th optical waveguides for each of the first to m-th optical groups, and among the first to m-th optical waveguides, The p-th optical waveguide is selected, and the output light from the p-th optical waveguide is radiated into the air to irradiate the reflection type diffraction grating spectroscope through a convex lens, and the diffracted light from the reflection type diffraction grating spectroscope Convex lens converges on a light receiving element array consisting of multiple light receiving elements and scans the output of the light receiving element array Then, the oscillation wavelength of the first semiconductor laser is detected, and the first semiconductor laser is provided with an amount proportional to the amount of displacement of the desired oscillation wavelength of the first semiconductor laser from the first reference light receiving element that receives the light. The oscillation wavelength is controlled so that the diffracted light enters the first reference light receiving element by returning, the output of the light receiving element array is scanned, and the same control is repeated up to the nth semiconductor laser. The mth optical waveguides are sequentially selected and the control of the semiconductor lasers of the p + 1th group to the mth group is repeated to set each reference light receiving element of the first group to the mth group to any light receiving element in the light receiving element array. be able to.

As one of the optical access networks using the wavelength division multiplexing method, there is a passive double star method in which an optical fiber branches in a dendritic manner from a node on the way. For example, as illustrated in FIG. 7, four wavelengths of λ ₁₁ to λ ₁₄ are wavelength-multiplexed on the station side and transmitted to the optical fiber 602, and the wavelengths of the wavelengths 607 to 610 are changed by the demultiplexer 605 which is a node on the way.
It is a method of branching into four optical fibers and delivering to each subscriber. The optical fibers 602 to 604 are bundled to form an optical cable, which is accommodated in a conduit or the like. In FIG. 7, four semiconductor lasers 6 for emitting four waves λ _{11 to} λ ₁₄ to be sent to the fiber 602 are emitted.
11 to 614 are collectively referred to as a first group of semiconductor lasers,
Similarly, the second group of semiconductor lasers oscillating at the wavelengths to be transmitted to the fibers 603 and 604 is similarly set to the second group.
Group 3 and group 3 semiconductor lasers. Using the wavelength stabilization device of the present invention, first, the oscillation wavelengths of the four semiconductor lasers of the first group are controlled, and then the semiconductor lasers of the second group are further controlled.
The semiconductor lasers of the group are controlled, and this cycle is repeated thereafter to collectively control the oscillation wavelengths of all the semiconductor lasers by one wavelength stabilizing device. It goes without saying that in an actual network, the number of semiconductor lasers 4 per group and the number 3 of groups can be further increased.

Embodiments of the present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram of an apparatus of an embodiment corresponding to claim 1 of the present invention, in which 1, 2, 3 are first, second and nth semiconductor lasers to be controlled, 4 , 5, 6 are transmission output lights from the semiconductor lasers 1, 2, 3 and 7, 8, 9 are control output lights from the semiconductor lasers 1, 2, 3 used to control the respective oscillation wavelengths. Is an optical multiplexer for multiplexing the control output lights 7, 8 and 9, 11 is an optical waveguide for guiding the output light from the optical multiplexer 10, 12 is a convex lens with a focal length f, 13 is a diffraction grating, Reference numeral 51 denotes an outgoing beam from the optical waveguide 11, 52 denotes an outgoing beam 51 which is a convex lens 12.
The collimated beam 53 is diffracted by the diffraction grating 13, 54 is a convergent beam of the diffracted light 53, 16 is a light receiving element array, 17 is an individual light receiving element of the light receiving element array, and 23 is a light receiving element array. Is the first switch circuit,
20, 21 and 22 are outputs from the light receiving elements 17, 18 and 19, 56 is a first switch of the first switch circuit 23, 57
Is the second switch, 24 is the output from the first switch, and 25
Is an output from the second switch, 26 is a first A / D converter, 27 is a second A / D converter, 28 is an output from the first A / D converter 26, 29 is an output from the second A / D converter 27, and 30 is A wavelength detection circuit, 31 is an output from the wavelength detection circuit 30, 32 is a wavelength comparison circuit, 33 is a reference wavelength information storage unit, 34 is an output from the reference wavelength information storage unit 33, 36 is a wavelength control circuit, and 35 is wavelength control. An output from the wavelength comparison circuit 32 which is an input to the circuit 36, 37 is a control signal from the wavelength control circuit 36, 38 is a second switch circuit, 58 is a switch, 39 is a control signal to the first semiconductor laser, and 40 is Control signal to the second semiconductor laser, 41 is a control signal to the nth semiconductor laser, 42 is a control circuit, 43 is a control signal from the control circuit 42 to the first switch circuit 23, and 44 is a wavelength detection time. 30 is a control signal, 45 is a control signal to the reference wavelength information storage unit 33, 46 is a control signal to the second switch circuit 38, and 47 is an output from the wavelength comparison circuit 32 which is an input to the control circuit 42. . Further, 61 is a power supply circuit which operates according to the control signal 39, 64 is its output, 62 is a power supply circuit which operates according to the control signal 40, 6
5 is its output, 63 is a power supply circuit which operates according to the control signal 41, and 66 is its output. The spectroscopic unit 200 surrounded by the alternate long and short dash line is shown enlarged in FIG.

Output light is obtained from each of the two end faces of the semiconductor laser. Output light from one end face is used for transmission and output light from the other end face is used for control for wavelength stabilization. The output light for transmission of the first semiconductor laser 1, the second semiconductor laser 2, and the nth semiconductor laser 3 to be controlled is 4, 5, and 6, and the output light 7, 8, 9 from the other end is for control. . The oscillation wavelengths of the first semiconductor laser 1 to the nth semiconductor laser 3 are in order from small to large, or from large to small. The control output lights 7, 8 and 9 are multiplexed by an optical multiplexer 10 such as a star coupler, and the control output light having n different wavelengths is guided to the optical waveguide 11. As shown in FIG. 2, the convex lens 12 having the focal length f is located at the distance f on the optical axis 55 from the exit end face 56 of the optical waveguide 11, and the diverging outgoing beam 51 is converted into a parallel beam 52 by the convex lens 12. To be done. The diffraction grating 13 is a so-called blazed grating in which the groove of the grating has a sawtooth shape, and the parallel beam 52 is incident on the normal line 14 of the diffraction grating 13 at an incident angle θ, and the light of wavelength λ is as shown in FIG. If it is diffracted at a diffraction angle θ _d , the diffraction order is m

## EQU1 ## mλ = d (sin θ + sin θ _d ) (1) holds. However, d is the pitch of the diffraction grating.
When the angular dispersion dθ _d / dλ is obtained from the equation (1), the following equation is obtained.

[Number 2] _{dθ d / dλ = m / dcos} θ d (2)

The diffraction grating 13 is arranged in a Littrow configuration, θ≈θ _d , and the position change dx on the light receiving element array 16 when the wavelength changes by dλ is

Equation 3] Since given by dx = fdθ _d (3), equation (2) and (3)

[Number 4] get dx / dλ = fm / dcos θ d (4). If the grating density of the diffraction grating 13 is 570 lines / mm, then d = 1.75 μm, λ = 1.55 μm, m =
2 and using θ≈θ _d , from equation (1), θ _d = 6
2.3 ° is obtained. Now, if an attempt is made to obtain a position change dx of 50 μm for a wavelength change dλ of 1 nm, equation (4)
To 35.5 mm as the value of the focal length f of the convex lens 12
Is required. The mode field radius ω of the optical waveguide 11 is set to 5
.mu.m, the parallel beam radius W is

From W = λf / πω (5), W = 3.5 mm is obtained. Total number of lattices N and W
Between

Since there is a relationship of dNcos θ = 2W (6), N = 8.62 × 103 is obtained from this. Resolution is

[Equation 7]           λ / δλ = mN (7) Therefore, δλ = 0.09 nm.

FIG. 3 shows each light receiving element of the light receiving element array 16,
The relationship between the output, the output terminal, and the switch is shown. Here, the pitch of the light receiving surface of the light receiving element is 10 μm, and the width of the light receiving surface is set to 8 μm. When the center of the light receiving element 201 is irradiated with the convergent beam 54 having a mode field radius of 5 μm, its wavelength is 1554.0.
If it is nm, dx / dλ = 50 μm / nm. Therefore, if the light receiving elements 202, 203, 204, 205 are sequentially irradiated, the wavelength interval Δλ = 0.2 nm, and the wavelengths are 1554.2 nm in order. , 1554.4 nm, 155
4.6 nm, 1554. nm. In reality, the spot 230 of the convergent beam 54 has two light receiving elements 203 and 20.
Irradiation may extend over 4 times. The wavelength detection method will be described including such a case. The light receiving element array 16 is M
The output 20 from the light receiving element 17 can be taken out from the terminal 217 in the first switch circuit 23, for example. The first switch circuit 23 has a first
There is a switch 56 and a second switch 57, and the first switch connects the first terminal 217 to the (M-1) th terminal 225,
The second switch 57 simultaneously selects from the second terminal 218 to the Mth terminal at a time interval of Δt, and the outputs of the adjacent light receiving elements are the outputs 24 and 25 from the first switch 56 and the second switch 57, respectively. As the first A / D converter 26,
It is guided to the second A / D converter 27. A CMOS switch can be cited as a switch having such a function. After kΔt time, the first switch 56 is connected to the terminal 222,
It is assumed that it is in contact with the second switch terminal 223. (K
-1) At the time of Δt, no output appears in both switches, but at the time of kΔt, the output is obtained from the second switch 57. The control circuit 42 thereby obtains (k + 1) Δt.
At this point, the first switch 56 is moved to the terminal 223 and the second switch 57 is moved to the terminal 224, and the wavelength is detected in this state.

The output obtained from the light receiving element 203 is A, and the output obtained from the light receiving element 204 is B. These outputs are digitized by the first A / D converter 26 and the second A / D converter 27, and the digitized signal A _d 2
8, B _d 29 is guided to the wavelength detection circuit 30. The wavelength detecting circuit 30 knows the wavelength λ ₂₀₃ of the light receiving element 203 based on the information from the control circuit 42 and performs the following calculation using the signals A _d 28 and B _d 29 to detect the wavelength λ _x .

Λ _x = B · Δλ / (A + B) + λ ₂₀₃ (8) where Δλ is the wavelength interval between the light receiving elements. If it is desired to obtain more accurately from λ _x, the separation width between the light receiving elements (2 μm in the case of FIG. 3) is corrected.

This output 31 is sent to the wavelength comparison circuit 32,
The reference wavelength information 34 is compared with the reference wavelength signal 34 registered in advance. In response to the difference signal 35, the wavelength control circuit 36 sends the control signal 37 to the second switch circuit 38.
Send to. The second switch circuit 38 connects the switch 5 to the terminal of the semiconductor laser 1 to be controlled by the signal 46 from the control circuit 42.
8 is closed, and the control signal 37 (control signal 39) is sent to the power supply circuit 61 for generating the current or voltage for controlling the wavelength of the semiconductor laser 1 and controls the output 64 thereof.
This output 64 is applied to a predetermined semiconductor laser 1.

If the semiconductor laser is a tunable laser that injects a wavelength controlling current, the injected current is generated as an output 64 in the power supply circuit 61, and the wavelength of the semiconductor laser is controlled by the temperature using a Peltier element. In the laser control circuit 61, a current flowing through the Peltier element is generated as an output.

The wavelength resulting from the control is detected by the wavelength detection circuit 30.
Detected by the wavelength comparison circuit 32 and compared with the reference wavelength 34 from the reference wavelength information storage unit 33, and the control is repeated until the wavelength difference reaches a desired value. Output 3 from wavelength comparison circuit 32
When the value of 5 becomes a value within a certain range, the wavelength control circuit 36 issues a control signal (command) 37 so that the current circuit 61 keeps holding the output 64 at that time, and at the same time, outputs a control end signal 59 of the semiconductor laser 1 to the control circuit. Send to 42. Control circuit 4
2 sends a signal 46 for controlling the next semiconductor laser 2 to the second switch circuit 38, and also sends a control signal 43 for activating the scanning of the first switch 56 and the second switch 57 to the first switch circuit 23. To do. After that, this is repeated. The oscillation wavelength of the first semiconductor laser 1 to the n-th semiconductor laser is controlled as one cycle, and this cycle is continuously or intermittently performed with a certain time interval.

FIG. 4 is a specific sectional perspective view of the light receiving element array 16. A PIN photodiode is used as the light receiving element. Consider a wavelength range of 1.55 μm. MOC
An n-type InGaAs layer 302 and an n-type InP layer 3 are formed on the n-type InP substrate 301 by using an epitaxial growth method such as VD.
Grow 03. For the n-type InP layer 303, a p-type InP region 304 is formed on the light-receiving surface 310 and the electrode portion 306 by diffusing Zn or the like. The diffusion front reaches the n-type InGaAs layer 302. In order to separate the light receiving elements, thin grooves are formed between the elements by ion etching or the like, and a polyimide 305 is embedded.
308 is an electrode on the n-type InP substrate side, and 307 and 309 are lead wires to the electrode. If the amplification band of 32 nm of the erbium-doped fiber laser amplifier (EDFA) is used as the wavelength band for wavelength multiplexing, the length of the light receiving element array 16 is 1.6 mm.

(Embodiment 2) FIG. 5 is a block diagram showing a device structure of an embodiment corresponding to claim 2 of the present invention. The semiconductor lasers to be controlled are the first group 141 to the m-th group 143.
Exists across. It is assumed that the oscillation wavelengths of the semiconductor lasers in each group are in the same band (for example, the amplification band of the EDFA). Reference numerals 101, 102 and 103 denote _first , second and n 1th semiconductor lasers 104, 105 and 10 of the first group.
6 is output light for transmission, 107, 108 and 109 are output light for control, and 110 is output light for control 107,
An optical multiplexer for multiplexing 108 and 109, 131 is a first optical waveguide for guiding the output light from the optical multiplexer 110, 1
First, second, third n _p semiconductor laser 11,112,113 Chapter p group (p is an integer of 1 ≦ p ≦ m), 114,11
5, 116 are output light for transmission, 117, 118,
Reference numeral 119 denotes the control output light, 120 denotes an optical multiplexer for multiplexing the control output light 117, 118, 119, 1
32 is a p-th optical waveguide that guides the output light from the optical multiplexer 120, and 121, 122 and 123 are the first, second and third members of the m-th group.
The n _m semiconductor laser, 124, 125, 126 and their transmission output light 127, 128, 129 and their control output light, 130 control the output light 127,128,1
An optical multiplexer for multiplexing 29, 133 is an optical multiplexer 13
It is the m-th optical waveguide that guides the output light from 0. The m optical waveguides from the first optical waveguide 131 to the mth optical waveguide 133 enter the optical switch 150 and receive the signal 4 from the control circuit 42.
8 selects the optical waveguide therein.

FIG. 6 shows an example of the optical switch. LiNb
A waveguide and a switch section (voltage application section) are formed on the O ₃ substrate. First input port 401, second input port 40
Input signals from the second input port 403, the third input port 403, and the fourth input port 404 are input to the first switch 405 and the second switch 40.
6, the signals of the first to fourth input ports can be selected for the output port 408 by the combination of ON and OFF of the third switch 407 (see Table 1).

[0024]

[Table 1]

That is, a group is selected by the optical switch 150. The control optical output of the semiconductor laser of the selected group is guided to the optical waveguide 151. Convex lens 12 with focal length f
Is at a distance f from the exit end face 15 of the optical waveguide 11, and the exit beam 51 from the exit end face 56 is converted into a parallel beam 52 by the convex lens 12. The parallel beam 52 is diffracted by the diffraction grating 13, and the diffracted beam 53 becomes a convergent beam 54 by the convex lens 12, becomes a spot light having the same radius as the mode field radius of the optical waveguide 151, and irradiates the light receiving element array 16. Hereinafter, the same control as that described in the embodiment corresponding to claim 1 is performed.

The first switch 56 of the first switch circuit 23
And the second switch 57, the outputs of two adjacent light receiving elements are simultaneously scanned at a time interval of Δt, and their outputs 2
4 and 25 are led to the 1st A / D converter 26 and the 2nd A / D converter 27, and an output is converted into a digital signal.
When no output appears at both switches at the time of (k-1) Δt, but an output is obtained from the second switch 57 at the time of kΔt, the control circuit 42 further causes the output by (k + 1) Δ. Both switches 56 and 57 are scanned and moved to the output terminals of the adjacent light receiving elements until time t, and the wavelength is detected in this state. Using the digital signal outputs 28 and 29, the equation (8) is calculated to detect the wavelength. This output 31 is sent to the wavelength comparison circuit 32, and the reference wavelength information storage unit 3
3 is compared with the reference wavelength signal 34 registered in advance, and the wavelength control circuit 36 sends a control signal 37 proportional thereto to the second switch circuit 38 in accordance with the difference signal 35. The second switch circuit 38 receives the signal 4 from the control circuit 42.
The switch of the semiconductor laser to be controlled is closed by the combination of the switch 191 for selecting the group in 6 and the switches 192, 193, 194 for selecting the semiconductor laser in the group, whereby, for example, the control signal 181 causes the power supply circuit 91 to change. Current or voltage output 9 for controlling the wavelength of a given semiconductor laser 121 accordingly.
4 is generated. This is an injection current if the semiconductor laser 121 is a tunable laser, and is a current passed through a Peltier element if the wavelength controlled semiconductor laser uses a Peltier element. The wavelength as a result of the control is detected by the wavelength detection circuit 30, and the reference wavelength information storage unit 3 is detected by the wavelength comparison circuit 32.
The reference wavelength 34 from 3 is compared, and the control is repeated until the wavelength difference reaches a desired value. When the output 35 from the wavelength comparison circuit 32 becomes a value within a certain range, the wavelength control circuit 36 issues a control signal (command) 37 so that the power supply circuit 61 keeps the output 64 at that time, and controls the semiconductor laser 121. An end signal 59 is sent to the control circuit 42. The control circuit 42 sends a signal 46 for controlling the next semiconductor laser 122 to the second switch circuit 38, and also controls the first switch circuit 23 to start scanning of the first switch 56 and the second switch 57. Is sent. After that, this is repeated. The control of the oscillation wavelength from the first semiconductor laser to the nth semiconductor laser is set as one cycle, and this cycle is continuously or intermittently performed at time intervals.

When the control of one group of semiconductor lasers is completed, the optical switch 15 is sent by the signal 48 from the control circuit 42.
0, the second switch 38 is controlled by the signal 46 to control the oscillation wavelength of the semiconductor laser of the next group. Controlling the oscillation wavelength of the semiconductor lasers 101 to 103 of the first group to the semiconductor lasers 121 to 123 of the mth group is one cycle,
Then, this cycle is performed continuously or intermittently at certain time intervals.

[0028]

As described above, according to the present invention,
It becomes possible to perform wavelength control at finer wavelength intervals, and when the wavelength characteristics of multiplexers / demultiplexers and filters placed in network nodes change depending on the environment, the reference wavelength of the wavelength to be controlled is As shown in FIG. 7, a compact and economical wavelength stabilizer that can be adaptively set with the precision of the wavelength interval and that can control the wavelength of each group of semiconductor lasers in the same wavelength region with a single device. Can be provided, which enables a dense and economical WDM optical communication system.

[Brief description of drawings]

1 is a block diagram of an apparatus of one embodiment corresponding to claim 1 of the present invention. FIG.

2 is a system diagram for explaining the structural function of the spectroscopic unit 201 enclosed by the alternate long and short dash line in FIG.

FIG. 3 is a diagram for explaining the relationship between each light receiving element of the light receiving element array 16 used in the present invention, its output, the light receiving element output terminal in the first switch circuit 23, and the first switch 56 and the second switch 57. is there.

FIG. 4 is a perspective sectional view showing a structural example of a light-receiving element array used in the present invention.

FIG. 5 is a block diagram showing a device configuration of an embodiment corresponding to claim 2 of the present invention.

6 is a plan configuration diagram of an optical switch 150 used in the embodiment of FIG.

FIG. 7 is a block diagram showing another embodiment of the present invention.

FIG. 8 is a schematic diagram for explaining a configuration of a diffraction grating spectroscope and an array waveguide portion in a wavelength stabilization device of a conventional technique.

FIG. 9 is a transmission loss characteristic diagram with respect to a wavelength of each arrayed waveguide of the conventional wavelength stabilization device.

FIG. 10 is a diagram for explaining the relationship between the position and wavelength of a convergent beam when a screen is placed perpendicularly to the optical axis at the position of the end face of the waveguide of the wavelength stabilizer of the prior art.

FIG. 11 is a cross-sectional structure diagram of an arrayed waveguide of a wavelength stabilization device of the related art.

[Explanation of symbols]

1 1st semiconductor laser 2 2nd semiconductor laser 3 nth semiconductor laser 4 Output light for transmission from 1st semiconductor laser 5 Output light for transmission from 2nd semiconductor laser 6 Output for transmission from nth semiconductor laser 3 Light 7 Control output light from first semiconductor laser 1 Control output light from second semiconductor laser 2 Control output light from nth semiconductor laser 3 Optical multiplexer 11 Optical waveguide 12 Convex lens 13 Diffraction grating 14 Normal line 15 of the grating surface of the analysis grating 13 Output end face 16 of the optical waveguide 11 Light receiving element array 17, 18, 19 Light receiving element 20 Output 21 from the light receiving element 17 Output 22 from the light receiving element 18 Output 23 from the light receiving element 23 1 switch circuit 24 output from the first switch 56 of the first switch circuit 23 output 25 from the second switch 57 of the first switch circuit 23 26 first A / D converter 27 Second A / D converter 28 Output from first A / D converter 29 Output from second A / D converter 30 Wavelength detection circuit 31 Output from wavelength detection circuit 32 Wavelength comparison circuit 33 Reference wavelength information storage unit 34 Reference wavelength Output 35 from information storage unit 33 Output 36 from wavelength comparison circuit 32 Wavelength control circuit 37 Output from wavelength control circuit 38 Second switch circuit 39 Control signal 40 to first semiconductor laser 1 40 Second semiconductor laser 2 Control signal 41 Control signal 42 to the nth semiconductor laser 3 Control circuit 43 Control signal 44 from the control circuit 42 to the first switch circuit 23 Control signal 45 from the control circuit 42 to the wavelength detection circuit 30 Reference wavelength information from the control circuit 42 Control signal 46 to the storage unit 33 Control signal 47 from the control circuit 42 to the second switch circuit 38 Output from the wavelength comparison circuit 32 which becomes power 48 Control signal 51 from the control circuit 42 to the optical switch 150 Output beam 52 from the optical waveguide 11 Parallel beam 53 output beam 51 is converted by the convex lens 12 Parallel beam 52 Diffraction grating 13 Diffracted beam 54 diffracted by 13 Diffracted beam 53 is converted by convex lens 12 Converged beam 55 Optical axis 56 First switch 57 Second switch 58 Switch 59 of second switch circuit 38 Control circuit 42 from wavelength control circuit 36 Signals 61 to 63 Power supply circuits 64 to 66 Outputs 71 to 73 from power supply circuits 61 to 63 Power supply circuits 74 to 76 Outputs 81 to 83 from power supply circuits 71 to 73 Power supply circuits 84 to 86 Power supply circuits 81 to 83 Output 91-93 of the power supply circuit 94-96 output 101 from the power supply circuit 91-93 First group first semiconductor laser 102 First group second semiconductor laser 103 First group n _1st semiconductor laser 104 Transmission output 105 of first semiconductor laser 101 Transmission output 106 of second semiconductor laser 102 ₁ Transmission output 107 of the semiconductor laser 103 Control output 108 of the first semiconductor laser 101 Control output 109 of the second semiconductor laser 109 Control output 110 of the n ₁ semiconductor laser 103 Optical multiplexer 111 First of the p-th group feed of the second semiconductor laser 113 first p group semiconductor laser 112 first p group of the n _p semiconductor laser 114 transmits output 116 the n _p semiconductor laser 113 of the transmitting output 115 second semiconductor laser 112 of the first semiconductor laser 111 Credit output 117 Control output 118 of the first semiconductor laser 111 Control output 119 of the second semiconductor laser 112 119th n _p semiconductor laser Transmission output of the n _m semiconductor laser 124 first semiconductor laser 121 of the second semiconductor laser 123 the m groups of the first semiconductor laser 122 the m groups of the control outputs 120 the optical multiplexer 121 first m group over THE 113 125 Transmission output 126 of the second semiconductor laser 122 Transmission output 127 of the _nm semiconductor laser 123 127 Control output 128 of the first semiconductor laser 121 Control output 129 of the second semiconductor laser 122 Control of the _nm semiconductor laser 123 Output 130 Optical Multiplexer 131 First Optical Waveguide 132 pth Optical Waveguide 133 mth Optical Waveguide 141 First Group Semiconductor Laser 142 pth Group Semiconductor Laser 143 mth Group Semiconductor Laser 150 Optical Switch 151 Optical Waveguide 161 First Control signal 162 to the first semiconductor laser 101 of the group First control signal 163 to the second semiconductor laser 102 of the group Control signal 171 to the n _1st semiconductor laser 103 of the group control signal 172 to the first semiconductor laser 111 of the pth group 172 control signal 173 to the second semiconductor laser 112 of the pth group nth _p semiconductor laser of the pth group Control signal 181 to the control signal 181 to the first semiconductor laser 121 of the m-th group 182 control signal 183 to the second semiconductor laser 122 of the m-th group control signal 191 to the _nm-th semiconductor laser 123 of the _m- th group Switches 192, 193, 194 for selecting a group in the second switch circuit 38. A switch 200 for selecting a semiconductor laser in each of the first group, the p-th group, and the m-th group in the second switch circuit 38. Spectral units 201 to 208 Light receiving elements 211 to 214 of light receiving element array 16 Respective outputs 215 from light receiving elements 201 to 204 Outputs 217 and 218 from light receiving element 208 Light reception Output terminals 221 to 226 in the first switch circuit for taking out the element outputs 20 and 21, respectively. Output terminals 230 in the first switch circuit for taking out the light receiving element outputs 211 to 215 and 22, respectively. A light receiving element array of the convergent beam 54. 16 spots on 16 n-type InP substrate 302 n-type InGaAs layer 303 n-type InP layer 304 p-type InP region 305 formed by diffusing Zn into the n-type InP layer 303 Polyimide 306 Electrode 307 Lead wire 308 Electrode 309 Lead wire 310 Light-receiving surfaces 401 to 404 First input port of optical switch to fourth input port 405 to 407 First switch to third switch in optical switch 408 Output port of optical switch 501 Optical grating of one array waveguide to diffraction grating Input waveguide 503 convex lens 504 diffraction grating 505 waveguide Output beam 506 emitted from 501 Parallel beam 507 obtained by converting output beam 505 by a convex lens Parallel beam 506 Diffracted beam 508 Diffracted by diffraction grating 504 Diffused beam 507 Converged beam 509-512 When the output waveguide 521 irradiates the center of the convergent beam, the region 522 whose wavelength corresponds to 1551.0 nm, and when the converging beam irradiates its center, the region 523 whose wavelength corresponds to 1551.2 nm When the center is illuminated, a region 524 whose wavelength corresponds to 1551.4 nm irradiates the center, and when the region 525 whose wavelength corresponds to 1551.6 nm illuminates the center, Region corresponding to wavelength of 1551.8 nm 26 When the convergent beam irradiates the center, its wavelength corresponds to 1552.0 nm 528 Array waveguide core 529 Array waveguide cladding 530 Air layer 601 Optical fiber cables 602 to 604 Optical fiber 605 Demultiplexer 606 ~ 609 Optical fiber

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinsuke Tanaka 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside International Telegraph and Telephone Corporation (72) Eiki Mimura 2-3-3 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 International Telegraph and Telephone Corporation (56) Reference JP 62-154685 (JP, A) JP 5-283784 (JP, A) JP 58-175884 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (2)

(57) [Claims] 1. A first to n-th oscillator having different oscillation wavelengths.
(Where, n is an integer of n ≧ 2) was combined by n and the controlled semiconductor laser, an optical multiplexer each portion of each of the output light of the n-number of the controlled semiconductor laser focus Means for guiding the wave output light to one optical waveguide, means for radiating the combined output light into the air from the one optical waveguide, and irradiating the reflected diffraction grating spectroscope through a convex lens, and the reflection diffraction means for converging the diffracted light from the grating spectrometer on a light receiving element array comprising a plurality of light receiving elements by the convex lens, by using two switches, Tonariru phase on the light receiving element array
The two switches select two light receiving elements, respectively.
On the light receiving element array by the two switches
Means for sequentially scanning a plurality of light receiving elements of the above to detect outputs corresponding to respective wavelengths by a plurality of convergent beam spots respectively corresponding to the first to nth semiconductor lasers; An amount proportional to the amount of positional deviation between the irradiation position on the light receiving element array of one convergent beam spot corresponding to one semiconductor laser and the predetermined reference position on the light receiving element array of the one convergent beam spot is set. Wavelength information by the wavelength compatible output and
Means for detecting as an error signal obtained by comparison with each predetermined reference wavelength information; and a means for returning the error signal to the one semiconductor laser so that the one converged beam spot is incident on the reference position. A unit for automatically controlling the oscillation wavelength of one semiconductor laser; and a unit for sequentially repeating the control for the n controlled semiconductor lasers in accordance with the scanning of the output of the light receiving element array, A wavelength stabilizing device, wherein the oscillation wavelengths of the n-th n semiconductor lasers can be set to desired values. 2. A first to m-th group (m = m-th group) (m = m-th group) consisting of n first to n-th (n is an integer of n ≧ 2) controlled semiconductor lasers, each group having a different oscillation wavelength. An integer of ≧ 2) and a part of each output light of each of the controlled semiconductor lasers of the first group to the m-th group is multiplexed into one multiplexer for each group.
Multiplexing the m-number of an optical multiplexer for the output of the m-number of the i (1 ≦ i ≦ m) th one of the optical multiplexer of the optical multiplexer multiplexing outputs selected one of the Means for guiding to the optical waveguide, means for radiating the combined output light from the one optical waveguide into the air, and irradiating the reflected diffraction grating spectroscope through a convex lens, and diffraction by the reflective diffraction grating spectroscope. means for converged on a light-receiving element array comprising a plurality of light receiving elements by a convex lens light, using two switches, Tonariru phase on the light receiving element array
The two switches select two light receiving elements, respectively.
On the light receiving element array by the two switches
Means for sequentially scanning a plurality of light-receiving elements of the above to detect outputs corresponding to respective wavelengths by a plurality of converging beam spots respectively corresponding to the first to n-th semiconductor lasers, and the n controlled semiconductor lasers of each group. Proportional to the amount of positional deviation between the irradiation position of one convergent beam spot corresponding to one of the semiconductor lasers on the light receiving element array and the predetermined reference position of the one convergent beam spot on the light receiving element array. The amount of wavelength
It is obtained by comparing the information with each predetermined reference wavelength information.
And a means for automatically controlling the oscillation wavelength of the one semiconductor laser so that the one converged beam spot is incident on the reference position by returning the error signal to the one semiconductor laser. And means for repeating the control of the output of the light receiving element array to the nth semiconductor laser according to scanning, and means for performing the control of the first to mth semiconductor lasers repeatedly. The wavelength stabilizing device is configured such that the oscillation wavelengths of the first to m-th group semiconductor lasers can be set to desired values.