JP2000035554A - Light wavelength adjusting device and light source using it, light wavelength separator, and multi-wavelength optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wavelength adjusting device having little temperature dependency in wavelength adjustment. SOLUTION: An error due to environmental temperatures becomes hard to occur in an adjusted wavelength by including a part of an optical output of an optical device branched by an optical coupler 11 into a wavelength variation control part 13 having an FBG part, further suppressing variations in the wavelength characteristic of fiber grating, which has originally little temperature dependency in a passing wavelength characteristic, by a wavelength variation control part 13, and adjusting the wavelength of the optical device A by a wavelength adjusting part 14 by using it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical wavelength adjusting device for adjusting the wavelength of light output from an optical device, and a light source, an optical wavelength separating device, and a wavelength division multiplexing optical communication system using the same.

[0002]

2. Related Background Art In recent years, there has been a demand for increasing the wavelength density in optical transmission due to the need for increasing the communication capacity of optical communication technology. For example, a general wavelength division multiplex transmission system (WD
In the optical communication system of M), optical signals from a plurality of light sources are multiplexed by an optical coupler or a WDM coupler and transmitted by a single optical fiber. In this optical communication system, the transmitting side transmits each optical signal separately for each wavelength, and the receiving side receives an optical signal of a specific wavelength demultiplexed by the optical wavelength demultiplexer.

However, in this system, for example, if the oscillation wavelength of light output from a light source is shifted, there is a risk that interference with light from another light source may occur. Therefore, it is necessary to accurately adjust the oscillation wavelength of the light source so that it is always constant. Therefore, in order to realize this, Patent Publication No. 254
There is an optical wavelength adjusting device using the optical filter described in No. 6151.

[0004]

However, in the past, a dielectric multilayer filter having a large temperature dependence of the wavelength characteristic has been used as an optical filter in such an optical wavelength adjusting apparatus, so that the accuracy of the wavelength adjustment has been reduced. Was bad. Further, in the conventional optical wavelength separation device, the optical wavelength adjustment device merely keeps the device temperature constant, and in particular, the adjustment for making the passing wavelength constant is not performed. However, in the above-described WDM optical communication system in which the wavelength is increased, if the wavelength of the light passed by the optical wavelength separation device is shifted, light of a desired wavelength cannot be passed, or light of another wavelength cannot be passed. For example, transmission quality may be degraded or transmission failure may occur.

As described above, in the WDM optical communication system, if the temperature error of the control wavelength is large in the optical wavelength adjusting device of each optical device, the WDM optical communication system has a problem that the transmission quality such as a transmission error is deteriorated. there were. In addition, C. Malo ct. Al ″ Laser wavelength s
tabilization using holographic filters ″ IEEE / LEOS
meeting on optical networks and their enablingtech
As shown in Nologics, Juiy 11-13, 1994, Lake Tahoe, NV, there is also an apparatus for fixing the oscillation wavelength of a laser using a crystal of LiNbO ₃ having a grating, so-called lithium niobate.

However, it is known that the Bragg wavelength of the grating has a temperature dependency in the above-mentioned device, and the temperature dependency is 0.01 nm / ° C. The crystal is mounted on a Peltier element, and a thermistor for detecting a temperature is provided. Further, a lens for collimating light output from an optical fiber, a beam slitter, a condenser lens, and two PDs are provided inside the device. Is required, and the optical system becomes complicated. Therefore, when this device is used, the device configuration becomes complicated and large, and as a result, there is a problem that the manufacturing cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an optical wavelength adjusting apparatus in which wavelength adjustment is less dependent on temperature. Another object of the present invention is to
An object of the present invention is to provide a light source having a simple configuration and a small variation in oscillation wavelength.

It is another object of the present invention to provide an optical wavelength demultiplexing apparatus having a simple configuration and a small fluctuation of a passing wavelength. Still another object of the present invention is to provide a WDM optical communication system in which transmission quality is less deteriorated.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a part of the light output from the optical device is output as a wavelength adjusting light by passing or reflecting, and the wavelength is adjusted. An optical filter unit in which the output level of the wavelength adjusting light changes with respect to a change in the wavelength of the operating light, and an output from the optical device such that the output level of the wavelength adjusting light output from the optical filter unit approaches a predetermined value. A wavelength adjusting unit for adjusting a wavelength of light to be applied, wherein the optical filter unit uses a fiber Bragg grating unit provided with a wavelength fluctuation suppressing unit. Is provided.

That is, a fiber grating, which is originally considered to have low temperature dependence of the passing wavelength characteristic, is further prevented from changing its wavelength characteristic by the wavelength fluctuation suppressing unit, and the wavelength is adjusted by using this to adjust the wavelength of the optical device. An error due to the environmental temperature hardly occurs in the adjusted wavelength. According to claim 2, the optical filter unit is configured by serially arranging two fiber Bragg grating units having different Bragg wavelengths from each other, and the wavelength adjusting unit adjusts the wavelength adjusting light output from the optical filter unit. A structure in which the wavelength of light output from an optical device is adjusted so that the output level approaches a peak value between the Bragg wavelengths of the two fiber Bragg grating sections, and a structure in which the two fiber Bragg grating sections are arranged in series. Can be obtained by forming two sets of gratings on one fiber, which simplifies the structure.

According to a third aspect of the present invention, the optical filter section is a resonator formed by arranging fiber Bragg grating sections in series, and the wavelength adjusting section outputs the wavelength adjusting light output from the optical filter section. Adjusts the wavelength of the light output from the optical device so that the output level of the fiber Bragg grating approaches the peak value corresponding to the Bragg wavelength of the fiber Bragg grating, and has a structure in which two fiber Bragg gratings are arranged in series. Can be obtained by forming two sets of gratings on one fiber, which simplifies the structure.

According to a fourth aspect of the present invention, the optical filter section includes one fiber Bragg grating section, and the wavelength adjusting section adjusts an output level of the wavelength adjusting light output from the optical filter section to a fiber Bragg grating section. By adjusting the wavelength of light output from the optical device so as to approach a predetermined level in the wavelength-dependent inclined portion, the structure becomes simple because only one fiber Bragg grating portion is required. In the wavelength adjusting unit, the adjustment is easy because the increase or decrease of the voltage value corresponds to the increase or decrease of the wavelength.

According to a fifth aspect of the present invention, the optical filter section includes a fiber Bragg grating section having a predetermined Bragg wavelength and using one of the two branches of the light output from the optical device as wavelength adjusting light. And the other light is passed or reflected as a reference light to a reference light passage section and output.The wavelength adjustment section outputs the wavelength adjustment light output from the fiber Bragg grating section. And a voltage value based on the difference between the output level of the reference light and the output level of the reference light output from the reference light passing unit, as an adjustment voltage value, so that the adjustment voltage value approaches a predetermined set voltage value. It adjusts the wavelength of the light output from the optical device and uses a part of the light branched as the reference voltage value. Can Nseru.

According to a sixth aspect of the present invention, there is provided a light source having an automatic output control unit, wherein a part of the output light is used as wavelength adjusting light, and the temperature of the optical device is controlled by the optical wavelength adjusting apparatus of the fifth aspect. Therefore, oscillation wavelength fluctuation can be reduced with a simple configuration. According to a seventh aspect of the present invention, there is provided an input unit to which a wavelength multiplexed light obtained by multiplexing a plurality of wavelengths of light is input, and an output unit that separates the wavelength multiplexed light into a plurality of lights of predetermined wavelengths and outputs the lights. 6. The optical wavelength demultiplexer according to claim 1, wherein a part of the light having any one of the wavelengths output from the output unit is used as wavelength adjusting light. By adjusting the wavelength of the light output from the optical wavelength separation device, the temperature dependence of the passing wavelength is reduced. Further, in an optical wavelength separation device, which is an optical device that handles light of a plurality of wavelengths, it is possible to adjust the passing wavelength for all the wavelengths of the optical device by applying feedback to light of one wavelength. A simple optical wavelength separation device can be provided.

According to an eighth aspect of the present invention, a plurality of light sources for outputting lights having different wavelengths from each other, a multiplexed optical transmission line for transmitting wavelength-division multiplexed light obtained by multiplexing the lights output from the plurality of light sources, 8. The optical wavelength separation device according to claim 7, wherein the wavelength multiplexed light transmitted through the optical transmission line is input, and is separated and output to light of different wavelengths, and the respective light output from the optical wavelength separation device is received. Each of the light sources uses part of its own output light as wavelength adjusting light, and the wavelength of the output light is adjusted by the optical wavelength adjusting device according to any one of claims 1 to 5. Is adjusted, the plurality of light sources are respectively adjusted to have the set wavelength. Also in the optical wavelength separation device, by using the optical wavelength separation device of the seventh aspect, the wavelength of light passing through the output unit is kept constant. Therefore, a wavelength division multiplexing optical communication system with less deterioration in transmission quality is provided.

In a ninth aspect, a plurality of light sources for outputting lights of different wavelengths from each other, a multiplexed optical transmission line for transmitting wavelength-division multiplexed light obtained by multiplexing lights output from the plurality of light sources, 8. The optical wavelength separation device according to claim 7, wherein the wavelength multiplexed light transmitted through the optical transmission line is input, and is separated and output to light of different wavelengths, and the respective light output from the optical wavelength separation device is received. The plurality of light sources are arranged on the same temperature control element, and the temperatures of the plurality of light sources are centrally managed, so that the wavelength of each light source is kept constant. . Also in the optical wavelength separation device, by using the optical wavelength separation device of the seventh aspect, the wavelength of light passing through the output unit is kept constant. Therefore, a wavelength division multiplexing optical communication system with less deterioration in transmission quality is provided.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an optical wavelength adjusting apparatus according to the present invention, a light source using the same, an optical wavelength demultiplexing apparatus, and a wavelength division multiplexing optical communication system will be described with reference to FIGS. (Basic Mode) FIG. 1 is a configuration diagram showing a basic configuration of an optical wavelength adjusting apparatus according to the present invention. In the figure, in the present invention,
A part of light output at a desired wavelength from the optical device A is
The light is split as wavelength adjusting light by the optical coupler 11 and input to the optical filter unit 12 of the present invention. Optical filter unit 1
In No. 2, in a fiber Bragg grating (FBG) unit 15 in which a grating is formed in the core of the optical fiber, the passing level of the wavelength adjusting light changes with respect to the wavelength change of the wavelength adjusting light and is output. Here, the Bragg wavelength of the FBG section 15 has little temperature dependence, but still has a temperature dependence of usually 0.01 nm / ° C. Therefore,
For example, since the change is 10 nm and the change is 0.1 nm, the amount of change is small, but for example, the IT of the wavelength between adjacent optical signals in a high-density wavelength division multiplexing communication system in the 1.55 μm band.
The U-recommendation is 0.8 nm, and even a slight wavelength shift due to a temperature change may cause deterioration of a transmission signal. Therefore, by providing the wavelength fluctuation suppressing unit 13, the wavelength characteristics of the wavelength adjusting light are not changed by the ambient temperature or the like. The wavelength adjusting unit 14 of the present invention photoelectrically converts the wavelength adjusting light passed through the optical filter unit 12 to obtain a voltage value corresponding to the passing level. Then, the wavelength adjustment unit 14 calculates an adjustment voltage value based on the voltage value, and outputs the adjustment voltage value from the optical device A such that the adjustment voltage value approaches a set voltage value corresponding to the set wavelength of the optical device A. Adjusts the wavelength of light.

Thus, in the basic configuration according to the present invention,
F, which is originally considered to have little temperature dependence of the transmission wavelength characteristic
A wavelength fluctuation suppressing unit 13 is provided in the optical filter unit 12 in which the BG unit 15 is used, and the wavelength of the optical device A is adjusted after the wavelength characteristics are not changed. Error due to the wavelength adjustment is less likely to occur, and the temperature dependence of wavelength adjustment can be reduced.

Here, the optical filter section 12 will be described in more detail. The Bragg wavelength of the grating formed in the FBG portion 15 is better than that of the dielectric multilayer film, but has a temperature characteristic. This is caused by the fact that silica, which is a material of the FBG portion, has a thermal expansion coefficient, and when the silica expands, the optical fiber expands in the longitudinal direction, so that the pitch of the grating also increases. This relationship is expressed as follows.

(Dλ _B / dT) = 2 {(dn / dT) + nα} where λ _B indicates the Bragg wavelength. Therefore, dλ _B / d
T indicates the temperature dependence of the Bragg wavelength. Λ is the pitch of the grating. The silica used for the core of the FBG portion 15 is usually doped with germanium. The temperature dependence of the refractive index is represented by dn / dT,
(Dn / dT) = 1.1 × 10 ⁻⁵ / ° C. n is FB
The refractive index of the core of the G section 15 is about 1.46.
α is the coefficient of thermal expansion, which is 5.2 × 10 ⁻⁷ / ° C. Therefore, the temperature dependence of the Bragg wavelength in the FBG section is
It is about 0.01 nm / ° C.

On the other hand, the Bragg wavelength also changes when a stress is applied. If a stress is applied in the direction in which the optical fiber is stretched in the longitudinal direction, the pitch of the grating becomes longer, so that the Bragg wavelength shifts to a longer wavelength. On the other hand, if a stress is applied in a direction to shrink the optical fiber, the pitch of the grating is narrowed, so that the Bragg wavelength is shortened.

As described above, the temperature characteristic of the FBG section 15 is such that the higher the temperature is, the longer the Bragg wavelength is, and the rate of change is constant at about 0.01 nm / ° C. Therefore, if a stress is applied in a direction opposite to the direction in which the FBG portion 15 extends with an increase in temperature, the change in the Bragg wavelength can be offset, and the optical filter 12 with low temperature dependence can be realized. This principle is used for the wavelength fluctuation suppression unit 13.

FIG. 2 shows the wavelength fluctuation suppressing section 13 shown in FIG.
FIG. 2 is a cross-sectional view showing a specific example of the first embodiment.
In the figure, a grating 15a is provided in the FBG section 15.
Is formed. In addition, as the wavelength fluctuation suppression unit 13,
Invar rod 16, fixtures 17 and 18 are used.
That is, for example, aluminum
(Α = 2.5 × 10^-Five/ ℃) and stainless steel
(Α = 1.7 × 10 ^-Five/ ° C)
8 is attached. Fixtures 17 and 18 each have a cross section
It is formed in an L-shape, and one end thereof has an invar rod 16
Are attached to each other and are opposed to each other.
The FBG unit 15 is attached. Here, the FBG section
15 and the Invar rod 16 have substantially equal thermal expansion coefficients
Fixtures 17 and 18 have larger thermal expansion
Have a number.

In the optical filter section 12 having the above configuration, when the ambient temperature rises, the FBG section 15 and the invar rod 16 tend to expand with substantially the same thermal expansion characteristics.
On the other hand, when the fixtures 17 and 18 having large thermal expansion thermally expand, a stress is generated in a direction to shrink the optical fiber, and the change in the Bragg wavelength of the grating 15a can be offset. The lengths of the fixing portions 17 and 18 are set in advance to a length that cancels out the expansion due to the thermal expansion characteristics of the FBG portion 15 and the invar rod 16 within the operating environment temperature range.

FIG. 3 shows a second example of the wavelength variation suppression unit 13.
It is sectional drawing which becomes an Example. In the following figure,
The same components as those in FIG. 2 are denoted by the same reference numerals for convenience of explanation. In the second embodiment shown in FIG. 3, the wavelength variation suppressing section 13 is composed of a silica tube 20 and a stainless steel tube 22.
And epoxy resins 21a, 21b, 21c. The FBG part 15 is arranged in the silica tube 20,
The FBG unit 15 is fixed in the silica tube 20. That is, on one side of the silica tube 20, the FBG portion 15 is fixed to the epoxy resin 21a, and the epoxy resin 21a
Is fixed in the silica tube 20. Silica tube 2
On the other hand, the FBG portion 15 is fixed in the stainless steel tube 22 with the epoxy resin 21b, and the stainless steel tube 22 is fixed to the epoxy resin 21c.
, And further fixed to the silica tube 20 to form the optical filter section 12.

In the FBG unit 15 and the wavelength fluctuation suppressing unit 13 having the above-described configurations, when the ambient temperature rises, the FB
The G portion 15 and the silica tube 20 tend to thermally expand with the same characteristic of thermal expansion coefficient. On the other hand, the stainless steel tube 22 thermally expands with a characteristic having a larger thermal expansion coefficient than these, and applies stress to the FBG portion 15, so that the elongation due to the thermal expansion characteristic of the FBG portion 15 can be canceled out. As a result, the change in the Bragg wavelength can be offset.

As described above, for the temperature compensation package in which the wavelength fluctuation suppressing section 13 is attached to the FBG section 15 and the package is configured to be capable of temperature compensation, for example, CW
Yoffe et.al, Technical Digest of OFC'95, WI4, pp134-1
35, 1995. Next, the FBG shown in FIG.
FIG. 4 shows an example of the relationship between the temperature of the portion 15 and the change in the Bragg wavelength.
Is shown in the relationship diagram. Referring to FIG.
The variation range of the Bragg wavelength in the range up to
The wavelength was 5 nm, and stable wavelength characteristics could be supplied without performing electrical temperature control.

As described above, according to the wavelength variation suppressing section 13 of the above embodiment, the stress that offsets the wavelength change of the FBG section 15 due to the temperature dependency is applied to the FBG section 15, so that the Bragg wavelength can be reduced with a simple configuration. Fixed so that the above F
The wavelength of the light passing through the BG unit 15 is further stabilized, and a desired oscillation wavelength can be obtained even if the laser light source is driven for a long time, for example.

Further, the wavelength fluctuation suppressing section 13 includes the FBG section 1
It is also possible to electronically control the temperature of 5 to fix the Bragg wavelength. FIG. 5 is a third embodiment showing the configuration of such a wavelength fluctuation suppressing unit 13. FB
The thermistor 23 and the Peltier device 24 are attached to the G unit 15, and based on the temperature detected by the thermistor 23, an automatic temperature control (ATC) circuit 25 controls the drive of the Peltier device 24 to adjust the temperature of the FBG unit 15. I have. The FBG unit 15 is stably fixed to, for example, a V-shaped groove of a fixture 26 placed on the Peltier element 24.

That is, in this embodiment, by stabilizing the temperature of the FBG section 15, the Bragg wavelength of the grating 15a can be fixed. Accordingly, in this embodiment, the temperature of the grating can be electrically adjusted to be kept constant, so that the transmission spectrum of the grating becomes constant, and the oscillation wavelength of the optical device, for example, the laser light source is fixed at a desired wavelength. Thus, effects similar to those of the first and second embodiments can be obtained.

Another example of the wavelength fluctuation suppressing unit 13 will be described in the first embodiment. In the following description, unless otherwise specified, the wavelength variation suppressing unit 13 is the one shown in the above example, and the Bragg wavelength of the FBG unit 15 is fixed thereby.

(First Embodiment) In this embodiment, as the optical filter section 12, two FBG sections having notch-type transmission wavelength-level characteristics and different or the same Bragg wavelength as shown in FIG. 27 and 28 are arranged in series, and the wavelength characteristics are stabilized by the wavelength fluctuation suppressing unit 13.

FIG. 7 shows a first example of an optical wavelength adjusting apparatus for an optical device according to the present invention using the optical filter section 12 shown in FIG.
FIG. 2 is a configuration diagram illustrating a configuration of an example. In the figure, in this embodiment, a laser such as a distributed feedback (DFB) laser is used as the optical device of the present invention, and a laser module 30 having the above laser and a laser module 30 are provided.
An optical coupler 11 for splitting an optical signal propagating through a pigtail fiber 31 which is an optical transmission line on the optical path of
An optical filter unit 12 including the wavelength adjustment lights 7 and 28 and a wavelength adjustment unit for adjusting the wavelength of light output from the laser of the laser module 30 based on the light passing through the optical filter unit 12 It comprises a unit 14 and an APC circuit 32 for controlling a laser injection current.

The wavelength adjusting unit 14 detects the wavelength adjusting light passing through the optical filter unit 12 and performs a photoelectric conversion on the PD 33.
ATC for controlling the temperature of the laser by adjusting the current to the Peltier element 36 based on the converted voltage signal.
It comprises a circuit 34 and a Peltier element 36.
As shown in FIG. 8, the laser module 30 outputs a light signal having a predetermined oscillation wavelength to the pigtail fiber 31 via an optical system 35 including an isolator, a lens, and the like, and outputs the light signal from the rear surface of the laser 30a. And a PD 37 for detecting light and performing photoelectric conversion.
The C circuit 32 controls the injection current based on the output voltage from the PD 37.

As shown in FIGS. 7 and 8, the light output from the laser 30 a is supplied from the pigtail fiber 31 to the optical coupler 1.
One is branched at 1, one propagates through the transmission line as an optical signal,
The other is input to the optical filter unit 12 as wavelength adjusting light. Each of the optical filters 12 has a grating 2
FBG units 27 and 28 having 7a and 28a and a wavelength fluctuation suppressing unit 13 are provided, and reflect a light wave around a Bragg wavelength. The reflection spectrum of the FBG units 27 and 28 is
In this embodiment, the two FBG units 2 depend on the diffraction grating spacing of the gratings 27a and 28a and the change in the refractive index.
It is created by making the Bragg wavelengths of 7, 28 close to each other. As a result, the two FBG units 27 and 28 created on the fiber
Is as shown in FIG. That is,
Let the Bragg wavelength of each FBG unit 27, 28 be λ1,
λ2, where λ is the wavelength of the intersection of this transmission spectrum,
If the wavelength characteristics of both gratings, their peak reflectivities and half-value widths are approximately equal, the wavelength λ is approximately halfway between λ1 and λ2. Then, when these two transmission spectra are combined, as shown in FIG. 10, the notch-type characteristic centering on the wavelength λ is exhibited, and the optical filter unit 12 becomes a notch-type transmission optical filter. The Bragg wavelength λ1,
λ2 has a relationship of λ1 <λ2.

Here, in the ATC circuit 34, first, the current to the Peltier element 36 is adjusted, and after the oscillation wavelength of the laser 30a is longer than λ1 and shorter than λ2, automatic temperature control is performed. The light that has passed through the optical filter unit 12 is PD
33 and photoelectrically converted into a voltage signal.
It has the characteristics shown in FIG. ATC circuit 3 of the present embodiment
In Step 4, the temperature of the laser 30a is controlled by adjusting the current injected into the Peltier element 36 so that the voltage signal becomes maximum (maximum value) in the wavelength range from λ1 to λ2.

As described above, in this embodiment, the temperature of the laser is controlled so that the wavelength of the light passing through the optical filter section 12 is maximized in the range of the two Bragg wavelengths. Is stable, the wavelength of the light passing therethrough is fixed, and a desired oscillation wavelength can be obtained even when driven for a long time. For this reason, when the optical wavelength adjusting apparatus of the present embodiment is used in, for example, a high-density wavelength division multiplexing communication system, the transmission signal is not degraded due to the wavelength shift, and the reliability of the transmission quality can be improved.

Further, in this embodiment, since a temperature sensor for detecting the temperature of the laser is not required, the manufacturing cost of the laser module can be reduced. Further, by forming the two gratings 27a and 28a on one optical fiber, the FBG units 27 and 28 can be formed, so that the configuration of the optical filter unit 12 is simplified.

In the present embodiment, the wavelength adjusting light is input to the optical filter section 12 after being branched by the optical coupler 11, but the present invention is not limited to this. For example, the present invention is applied to the pigtail fiber. And the light passing through the FBG units 27 and 28 may be branched by the optical coupler 11 and input to the wavelength adjustment unit 14.
As in the embodiment, the oscillation wavelength of the laser 30a can be stabilized.

In this embodiment, the FBG units 27 and 28
Are connected in series. However, the present invention is not limited to this. For example, the wavelength adjusting light is passed through each of the FBG units 27 and 28 and converted into an electric signal. Can be combined, or the reflection spectrum of the Bragg wavelength from these gratings can be combined.

FIG. 12 is a configuration diagram showing a configuration of an optical wavelength adjusting apparatus configured to extract an optical output from a rear output of a laser as a second embodiment. In the following drawings, the same components as those in the first embodiment are denoted by the same reference numerals for convenience of explanation. In FIG. 12, in the present embodiment, in order to drive and control the laser by the APC circuit 32, the light output from the laser module 30 is monitored by the PD 37. Therefore, in the present embodiment, the light is taken out of the laser module 30 by a pigtail fiber provided on the optical path of the light output on the rear surface of the laser, and the light is branched by the optical coupler 11. One of the branched lights is the first light.
It is used for controlling the APC circuit 32 via the PD 37 as in the embodiment. The other light is input to the optical filter unit 12, passes through the two FBG units 27 and 28 whose wavelength characteristics have been stabilized by the wavelength fluctuation suppressing unit 13, and is converted into a voltage signal by the PD 33. The ATC circuit 34 controls the temperature of the laser by adjusting the current injected into the Peltier element 36 so that the voltage signal becomes maximum in the range of wavelengths λ1 to λ2.

As described above, in this embodiment, the light output is extracted from the rear output of the laser, and the wavelength of the light passing through the FBG section is maximized in the range of two Bragg wavelengths.
Since the temperature of the laser is controlled, the oscillation wavelength of the laser is stable, the wavelength of the light passing therethrough is fixed, and a desired oscillation wavelength can be obtained even when the laser is driven for a long time, as in the first embodiment. And so on.

The laser module 3 shown in FIG.
0, optical filter unit 12, PD33, 37 and optical coupler 1
One function may be configured as one unit. For example, as shown in FIG. 13, the laser 30a is fixed on the Si substrate 38, and the rear facet of the laser 30a and the optical waveguide 39 made of silica are directly connected without an optical system. The optical waveguide 39 is branched into two parts, one of which is connected to the PD 37 connected to the APC circuit 32, and the other is connected to the PD 33 via two FBG parts 40 and 41 formed on the silica optical waveguide 39. According to the principle shown in the second embodiment, the temperature of the laser 30a is controlled by adjusting the current injected by the ATC circuit 34 into the Peltier element 36 using the signal detected by the PD 33.

In the third embodiment, the same effects as those of the first embodiment can be obtained, and the components of the optical wavelength adjusting apparatus according to the present invention can be housed in one unit. The size and weight can be reduced. In addition, since the Peltier element 36 functions as a wavelength fluctuation suppressing unit that stabilizes the wavelength characteristics of the FBG units 40 and 41, it is not necessary to separately provide a wavelength fluctuation suppressing unit.

Here, examples of the wavelength fluctuation suppressing unit 13 in FIGS. 6 to 12 will be described below. In the examples of FIGS. 14 and 15,
For example, the thermistor 42,
43 and Peltier devices 44 and 45, respectively,
Based on the temperatures detected by the thermistors 42 and 43, the ATC circuits 46 and 47
Is controlled so that the temperatures of the FBG units 27 and 28 become constant. The optical fiber of the FBG section is stably fixed to the V-grooves of the fixtures 48, 49 placed on the Peltier elements 44, 45.

As described above, in this embodiment, the FBG unit 2
By stabilizing the temperatures of 7, 28, the wavelength characteristics of the gratings of the two FBG portions can be stabilized. Further, as shown in a second example of the wavelength fluctuation suppressing unit 13 in FIG. 16, two FBG units 27 and 28 are mounted on one Peltier element 44, and ATC is performed based on the temperature detected by the thermistor 42. The circuit 46 may be configured to drive and control the Peltier element 44 to adjust the temperature of the wavelength fluctuation suppression unit 13. In this case, as in the above embodiment, the oscillation wavelength of the optical device can be fixed at a desired wavelength and the number of parts can be reduced by adjusting the temperature of the grating of the FBG units 27 and 28 to be constant. it can.

By the way, it is known that the FBG portion changes the Bragg wavelength even when a stress is applied. Therefore, as shown in a third example of the wavelength variation suppressing unit in FIGS. 17 and 18, the FBG units 27 and 28 are housed in a housing 50 in which external stress is sufficiently blocked, and In the body 50, a fixture 5 for fixing the optical fibers to the insertion ports 51, 52 of the housing 50 so that no stress is applied in the longitudinal direction of the optical fibers forming the FBG portions 27, 28.
3, 54 are arranged. Further, a fixing tool 55 having a V-groove in the housing 50 so that the FBG portions 27 and 28 are not bent.
Are arranged and the FBG units 27 and 28 are fixed.

Thus, since the FBG portions 27 and 28 are configured so that no stress is applied from the outside, the Bragg wavelength is kept constant, and the oscillation wavelength of the laser light source can be fixed at a desired wavelength. Further, by utilizing the characteristic that the Bragg wavelength of the FBG section changes due to stress, as shown in a fourth example of the wavelength fluctuation suppressing section 13 in FIG.
8, the piezoelectric elements 56 and 57 are attached to the outer peripheral surfaces of the gratings 27a and 28a, and the piezoelectric elements 56 and 57 are operated by applying a voltage V from DC voltage sources 58 and 59,
The gratings 27a and 28a are configured to apply stress in the vertical direction.

Therefore, by changing the voltage applied from the DC voltage source, the stress applied to the FBG portions 27 and 28 can be changed, whereby the FBG portions expand and contract in the vertical direction, so that the gratings 27a and 28a Is changed, and the oscillation wavelength can be changed to set the desired wavelength. FIG. 20 shows a crystal obtained by changing the crystal of the piezoelectric element shown in FIG. 19 by 90 degrees. Also in the fifth example of the wavelength fluctuation suppressing unit 13, the piezoelectric element 56,
The operation is performed by applying a voltage V from a DC voltage source (not shown) to the 57, whereby in the present embodiment, the stress in the longitudinal direction of the grating changes, and the Bragg wavelength can be stabilized.

In the present invention, the notch type transmission wavelength-
In order to form an optical filter section having a level characteristic, in addition to an apparatus for obtaining a desired oscillation wavelength by using an FBG section in which gratings having different Bragg wavelengths are connected in series as shown in the above embodiment, for example, an FBG section Are formed by gratings having the same constant pitch,
It is also possible to make the resonator with a resonator that transmits light in a narrow band, such as a fiber grating Fabry-Perot filter.

For example, a π / 2 phase shift fiber grating Fabry-Perot filter will be described. As shown in FIG. 21, an FBG in which gratings 61, 61 are formed at a constant pitch in a core of an optical fiber 62 is shown.
In the sections 60, 60, by providing a blank having a length Lc between the gratings 61, 61, the FBG sections 60, 60 constitute a Fabry-Perot resonator. At this time, the Bragg wavelength λB of each of the gratings 61, 61 is expressed as λB = 2nav, where 周期 denotes the period of the grating and nav denotes the average refractive index of a fiber core (not shown) in which the grating is formed. The transmittance T of this fiber grating Fabry-Perot filter is: T = 1 / ｛1 + 4 | f11 | ² | f12 | ² cos ² (βLc +
φ)｝ where f11 = cosh (γz) −j (δ / γ) sin
h (γz) f12 = − (κ / γ) sinh (γz) φ = tan ⁻¹ ｛(δ / γ) tanh (γL)｝ κ = πΔn / λ γ = √ (κ ² −δ ² ) δ = 2navπ {(1 / λ) − (1 / λB)}. β is a propagation constant and is represented by β = 2πnav / λ.

When the transmittance T becomes 1, the transmittance is maximum, and theoretically light passing through the filter passes without loss. The center of this filter is the Bragg wavelength λB. As can be seen from the above transmittance equation, co
When s (βLc + φ) = 0, the transmittance becomes maximum.
Since φ = 0 at the Bragg wavelength, the condition may be the following relationship.

ΒLc = (m + ／) π where:
m = 1, 2, 3,... That is, the resonator length Lc of the Fabry-Perot resonator may have the following relationship. Lc = (m + ／) Λ When this condition is substituted into the above equation for the transmittance T, the following is obtained. T = 1 / [1 + 4 | f11 | ² | f12 | ² cos ² } (m +
1/2) π · λB / λ + φ}] Here, for example, 1550nm the Bragg wavelength .lambda.B, the refractive index change Δn of 5 × 10 ^{- 4,} and the length between the grating 61 and 61 for calculating the equation as 2 mm, FIG. The relationship between the transmitted light and the wavelength shown in 22 is obtained.

Therefore, in this embodiment, instead of the two FBG portions having different Bragg wavelengths shown in the respective embodiments of FIGS. 7 to 13, the FBG portions are formed by gratings 61 having the same Bragg wavelength at a constant pitch. 60 and 60 are formed to allow light of a predetermined band including a Bragg wavelength by the laser light emitted by the laser to pass, and the signal level of the light (corresponding voltage signal) passed within the predetermined band to reach a maximum value Thus, by controlling the temperature of the laser, the same effects as in the above embodiments can be obtained. That is, FB
The laser can be controlled so as to have a signal level of the Bragg wavelength which is the center wavelength of a predetermined band passing through the G section.

The control of the Bragg wavelength of the FBG section shown in FIG. 21 can be performed as in the embodiments shown in FIGS. 14 to 20. In this case, the same effect as in the above embodiments can be obtained. be able to. Further, since the diffraction grating intervals of the gratings 61, 61 are the same between the FBG units 60, 60, the manufacture of the FBG units 60, 60 is easy.

(Second Embodiment) FIG. 23 is a block diagram showing a fourth embodiment of the optical wavelength adjusting apparatus for an optical device according to the present invention. In the figure, in this embodiment, an optical signal output from a laser module 30 having a laser such as a DFB laser that is an optical device and oscillates in a single longitudinal mode is, for example,
The light propagates through the pigtail fiber 31, is branched by the optical coupler 11, takes in the branched wavelength adjusting light by the optical filter unit 12, detects the light passing through the optical filter unit 12, and
The ATC circuit 34 and the Peltier device 63 control the temperature of the laser based on the converted voltage signal.

The optical filter section 12 includes, for example, FIGS.
Alternatively, as shown in FIG. 5, an FBG unit 15 and a wavelength fluctuation suppressing unit 13 for stabilizing the wavelength characteristics are provided. PD 33, ATC circuit 34, and Peltier element 63
Constitute the wavelength adjustment unit 14. ATC circuit 34
Is a voltage converter 34a that converts a signal from the PD 33 into a voltage signal, a monitor circuit 34b that detects the maximum level and the minimum level of the converted voltage signal, and a reference that adjusts a reference voltage that is an arbitrary reference level. Voltage regulator 34c
And a differential amplifier 34d that compares the voltage signal from the voltage converter 34a with the reference voltage, and adjusts the current to the Peltier element 63 based on the converted voltage signal to control the temperature of the laser module 30. And a Peltier current control circuit 34e.

The laser module 30 is connected with an APC circuit 64 for controlling the injection current to the laser and keeping the optical output constant, and a modulator 65 for outputting a modulation signal.
Optical communication by the laser module 30 is enabled.
It is known that the temperature dependency of the laser oscillation wavelength is 0.1 nm / ° C., and an optical signal from the laser module 30 is branched from a pigtail fiber 31 by an optical coupler 11, and one of the optical signals is an optical signal. And the other is input to the optical filter unit 12 as wavelength adjusting light.

The grating 15a exhibits a notch type transmission wavelength-level characteristic having a Bragg wavelength at the center, and the FBG section 15 is a notch type transmission type optical filter. For this reason, as shown in FIG. 24, the transmitted light of the FBG unit 15 has the smallest transmitted light power at the Bragg wavelength, and has wavelength dependence having inclined portions on both sides of the Bragg wavelength. In other words, the optical filter can be configured such that the set wavelength is located at a part of one of the inclined portions 66 formed on both sides of the Bragg wavelength in the transmission wavelength-level characteristic.

The light transmitted through the FBG unit 15 is transmitted to the PD3
3, the PD 33 outputs a current based on the transmitted light power. When the current is converted into a voltage by the voltage converter 34a, the output voltage reflects the transmission spectrum of the grating 15a as shown in FIG. It has wavelength dependence. Referring to FIG. 25, at the Bragg wavelength, since the transmitted light power is the smallest, the detected output voltage is at the minimum level. In this embodiment, this voltage is set to Vmin. On the other hand, at a wavelength at which the reflection by the grating disappears, the transmitted light power is large, and the detected output voltage is at the maximum level. In this embodiment, this voltage is set to Vmax.

The reference voltage Vref corresponding to the set wavelength is defined in the voltage characteristic in which the voltage change with respect to the wavelength between Vmin and Vmax has a slope shape. At this time, Vref has a relationship of Vmin <Vref <Vmax. In the present embodiment, before controlling the temperature of the laser, the Peltier current control circuit 34e is controlled by the monitor circuit 34b.
By operating the Peltier element 63, the oscillation wavelength of the laser in the laser module 30 is changed, and
Measure n and Vmax. In this embodiment, the above V
The reference voltage adjuster 34c sets an intermediate voltage between min and Vmax, (Vmax-Vmin) / 2, as a reference voltage.

Therefore, in this embodiment, the control wavelength is prevented from shifting to a wavelength shorter than the Bragg wavelength or to a wavelength at which there is no reflection. The differential amplifier 34d outputs a difference between the reference voltage from the reference voltage regulator 34c and the voltage signal from the voltage converter 34a, and outputs the voltage signal ΔV
Has wavelength dependence as shown in FIG.

The Peltier element 63 has a characteristic that the temperature rises or falls depending on the polarity of the current to be injected.
This characteristic differs depending on the connection method between the Peltier element and the circuit, but in this embodiment, the temperature decreases when a positive current is applied, and the wavelength of the laser shifts to the short wavelength side, and when a negative current is applied, the temperature decreases. And the wavelength of the laser shifts to the longer wavelength side.

The ATC circuit 34 performs feedback control so that the voltage signal ΔV becomes 0. That is, when the oscillation wavelength shifts to the longer wavelength side, ΔV is output as a positive value.
When input to e, a positive current flows through the Peltier element 63 to lower the temperature, and the wavelength of the laser shifts to the shorter wavelength side. When the oscillation wavelength shifts to the short wavelength side, ΔV is output as a negative value. Therefore, when this voltage signal ΔV is input to the Peltier current control circuit 34e, a current having a negative value is supplied to the Peltier element 63. The temperature of the laser rises and the wavelength of the laser shifts to the longer wavelength side.

Therefore, in this embodiment, a part of the output light of the laser module 30 is used as the wavelength adjusting light and the optical coupler 11 is used.
And transmitted through the FBG unit 15, and the transmitted light is
While being detected by the TC circuit 34 and converted into a voltage signal,
The temperature of the laser is controlled by comparing the reference voltage obtained from the light transmission spectrum of the FBG unit 15 and controlling the injection current of the Peltier element 63 by using the difference. , A desired oscillation wavelength can be obtained even if the device is driven for a long time.

In this embodiment, the FBG unit 15 and the AT
Since the oscillation wavelength of the laser is stably controlled by using the C circuit 34 and the Peltier element 63, the number of parts is reduced, whereby the oscillation wavelength can be adjusted with a simple configuration that is small and lightweight, and the components can be adjusted. The production cost can be reduced along with the reduction of the cost. Therefore, when the oscillation wavelength adjusting device of the present embodiment is used in, for example, a high-density wavelength division multiplexing communication system, deterioration of a transmission signal due to a wavelength shift is eliminated, and reliability of system transmission can be improved.

In the present embodiment, the reference voltage is set to an intermediate voltage between Vmin and Vmax of the light transmission spectrum of the FBG portion. However, the present invention is not limited to this, and the reference voltage is set to an arbitrary level between Vmin and Vmax. It is possible to set a reference voltage, and in this case also, the oscillation wavelength of the laser can be controlled stably similarly to the embodiment. Further, in the present embodiment, the optical signal is input to the FBG unit after being branched by the optical coupler. However, the present invention is not limited to this. For example, instead of the pigtail fiber, the FBG unit 15 according to the present invention Even when the laser is connected on a road and the light passing through the FBG section is branched by an optical coupler and input to the PD, the oscillation wavelength of the laser can be stabilized.

In the present invention, the calculation of the Vmin and Vmax and the reference voltage, and the setting of the reference voltage are performed by the monitor circuit 3.
The measurement can be performed manually based on the measurement value measured in 4b or automatically using a microcomputer or the like.

(Third Embodiment) By the way, even when the output light level from the laser by the APC circuit is fixed, the output light level is not completely constant but slightly fluctuates up and down. That is, as shown in FIG. 23, in the optical wavelength adjusting apparatus using only a part of the output light as the wavelength adjusting light and using a constant voltage value as the reference voltage, the level of the output light passing through the optical filter can be increased or decreased. This is because the fluctuation appears as an error component of the optical wavelength to be controlled as it is, and therefore, the stability of the optical wavelength output from the laser is slightly lowered.

FIG. 27 is a configuration diagram showing the configuration of a fifth embodiment of the optical wavelength adjusting apparatus capable of canceling such an error component of the optical wavelength. In the figure, in the present embodiment, an automatic output control unit of the present invention is configured, and an APC circuit that controls a laser injection current in the laser module 30 is provided.
A part of the optical signal output from the laser module 30 is branched by the optical coupler 11, and the branched light is branched by the optical coupler 67 and output to the optical filter unit 12. The optical filter unit 12 allows one of the branched lights to pass through the FBG unit 15 as wavelength adjusting light,
The other light is passed as reference light through the FBG unit 68 constituting the reference light passing unit of the present invention.

The FBG units 15 and 68 have different Bragg wavelengths, and are set so that, for example, the wavelength characteristics of the transmittance partially overlap as shown in FIG. Here, FIG.
8 is an FBG 15 when the half width Δλ is 0.4 nm and the transmittance at the Bragg wavelength is 0.5.
4 shows the relationship between the transmittance and the wavelength of the FBG 68. In the wavelength adjusting unit 14, the light passing through the FBG units 15, 68 is
The signals are photoelectrically converted by D33 and D69, and the converted signals are converted into voltage signals by voltage converters 34a and 34f. Then, when the signal is amplified by the differential amplifier 34d at an appropriate multiplication factor and the difference between them is detected, the difference voltage has a wavelength characteristic as shown in FIG. The voltage signal is used as an adjustment voltage signal for controlling the Peltier element 63, and the wavelength of light output from the laser module 30 is adjusted so that the voltage value of the voltage signal approaches a predetermined set voltage value.

As described above, in this embodiment, a part of the output light is branched into both the wavelength adjusting light and the reference light to obtain a difference voltage, and the difference voltage is applied to the Peltier device attached to the laser module 30. The signal is fed back to the Peltier current control circuit 34e as a signal for controlling the P. 63. Therefore, the wavelength error due to the level fluctuation of the output light can be canceled when the difference voltage is obtained, and the wavelength of the light output from the laser module 30 can be controlled accurately.

FIG. 30 shows the configuration of a sixth embodiment of the optical wavelength adjusting apparatus in which an optical attenuator 70 is provided instead of the FBG section 68 constituting the reference light passing section shown in the fifth embodiment of FIG. It is a block diagram. In this embodiment, the output level of the optical attenuator 70 is adjusted so that the wavelength of the optical signal is
When the Bragg wavelength is equal to 5, the light receiving level of the light passing through the optical attenuator 70 is set to be higher than the light receiving level of the light passing through the FBG unit 15.

As a result, the characteristics of the voltage signal indicating the differential voltage from the differential amplifier 34d and the wavelength are as shown in FIG. 31, and the voltage signal becomes "0" only at a predetermined wavelength from the Bragg wavelength. This is the case where the wavelength becomes farther to the long wavelength side or the short wavelength side. The voltage signal from the differential amplifier 34d is fed back to the Peltier current control circuit 34e using the tilt characteristic of the voltage signal with respect to the wavelength, to control the temperature of the laser.

As a result, in this embodiment, the oscillation wavelength from the optical device can be adjusted to a wavelength at which the difference voltage becomes “0”. Therefore, as in the fifth embodiment, the wavelength error due to the level fluctuation of the output light is reduced. Is taken, the light wavelength is stabilized, and the light wavelength can be controlled with high accuracy. FIG. 32 is a configuration diagram showing the configuration of a seventh embodiment of the optical wavelength adjusting device in the case where a high branching ratio coupler that changes a light branching ratio is used as the optical coupler 67, for example. In the figure, in the present embodiment, the optical coupler 67 and the PD 69 are directly connected, and, for example, when the reflectance of the FBG unit 15 is 50%, the wavelength within the laser module 30 is set to a wavelength that is half the half-width from the Bragg wavelength. In order to fix the oscillation wavelength of the laser, the branch ratio of the high branch ratio coupler 67 is set to 3: 2,
By making the light level incident on the FBG unit 15 higher, a voltage signal of a difference voltage having a wavelength characteristic as shown in FIG. 31 is created.

As described above, in this embodiment, the optical coupler 67
If the branching ratio is changed, the reference light can be detected without providing an FBG portion or an optical attenuator as the reference light passing portion, and the oscillation wavelength from the optical device can be adjusted to a wavelength at which the difference voltage becomes “0”. Therefore, the same effects as those of the fifth and sixth embodiments can be obtained, and the number of components can be reduced.

Further, in the present invention, it is possible to provide an offset mechanism in a differential amplifier that generates and outputs a differential voltage signal. In this case, by adjusting the offset, the zero point of the difference voltage can be finely adjusted, and the wavelength at which the difference voltage becomes “0” can be adjusted. Therefore, in the present embodiment, the light wavelength can be controlled more accurately than in the fifth to seventh embodiments shown in FIGS. 27, 30 and 32.

(Fourth Embodiment) Further, the optical wavelength adjusting devices shown in the above-described basic mode and the first to third embodiments have a temperature dependency of an arrayed waveguide grating (AWG), a dielectric multilayer film or the like. It can also be used for an optical wavelength separation device provided with a WDM filter 71 having the same. FIG. 33 is a configuration diagram showing an example of this case. In this embodiment, a case where AWG is used will be described. In the figure, an input waveguide 72 constituting an input section of the present invention and an output waveguide 73 also constituting an output section of the present invention are arranged in a WDM filter 71, and a plurality of wavelengths λ1
Λn are multiplexed into the input waveguide 72.
The wavelength-division multiplexed light is split by the slab waveguides 74 and 75 for interference and the arrayed waveguide 76 and output from the output waveguide 73 to different optical fibers for each wavelength. Reference numeral 79 denotes a half-wave plate, which adjusts the phase of light.

In this embodiment, the optical tap 77 is connected to the optical fiber transmitting the optical signal of the wavelength λn among these optical fibers, and the optical signal is taken out.
The light is split into two at 8 and passes through the temperature compensating FBG units 15 and 68 having wavelength characteristics different from the Bragg wavelength shown in FIG. Then, photoelectric conversion is performed by the PDs 33 and 69, and the AT
Each voltage signal is detected from the signal converted by the C circuit 34, and a difference voltage is further detected from each of the voltage signals.
The temperature of the WDM filter 71 is controlled by controlling the Peltier element 63 attached to the WDM filter 71 based on the difference voltage signal.

Thus, in this embodiment, the pass wavelength can be adjusted for all the wavelengths of the WDM filter by applying feedback so that the difference voltage becomes “0” for light of one wavelength. An optical wavelength separation device having a simple structure can be provided. Further, the wavelength error due to the level fluctuation of the output light can be canceled when the difference voltage is obtained, so that the light wavelength to be filtered is stabilized.

In the case of a WDM filter using a dielectric multilayer film, the wavelength characteristics can be adjusted by changing the angle of the filter. Therefore, in the case of this WDM filter, by configuring the difference voltage signal to be fed back to the control mechanism for adjusting the angle of the filter, the wavelength error can be reduced when the difference voltage is obtained as in the above embodiment. The light wavelength is stabilized by canceling, and the light wavelength can be controlled with high accuracy.

(Fifth Embodiment) It is also possible to construct a WDM optical communication system using the laser modules shown in the first to third embodiments and the optical wavelength separation device shown in the fourth embodiment. It is. FIG. 34 is a configuration diagram showing one example. In the figure, each of laser modules 81 to 8n constituting a light source of the present invention outputs light of different wavelengths, and a part of its own output light is used as wavelength adjusting light. The wavelength of the output light is adjusted by the optical wavelength adjusting device described in any one of the embodiments. Therefore, a plurality of laser modules 81 to 8
n is adjusted so as to be the set wavelength. The light output from the plurality of laser modules 81 to 8n is
The light is multiplexed by the WDM coupler 90 and transmitted to the multiplex optical transmission line 91 as wavelength multiplexed light. The wavelength-division multiplexed light transmitted through the multiplex optical transmission line 91 is input to the WDM filter 92 configured by the optical wavelength demultiplexer shown in the fourth embodiment, and is separated into light of different wavelengths. It is input to each of the photoelectric converters 101 to 10n that constitute the optical receiver. The photoelectric converters 101 to 10n receive the light of each wavelength output from the WDM filter 92,
Output as an electric signal.

As described above, in this embodiment, on the transmitting side, each laser module 81 is controlled by the optical wavelength adjusting device.
The oscillation wavelength of the laser within ~ 8n can be adjusted to a predetermined wavelength,
And on the receiving side, since the passing wavelength can be adjusted by the optical wavelength demultiplexer and separated into light of different wavelengths,
Wavelength errors due to environmental temperature fluctuations can be suppressed. Therefore, it is possible to provide a wavelength division multiplexing optical communication system with little deterioration in transmission quality.

(Sixth Embodiment) Further, a WDM optical communication system can be constructed by using a plurality of laser modules arranged on the same temperature control element and the optical wavelength separation device shown in the fourth embodiment. It is possible. FIG. 35 is a configuration diagram showing one example. In the figure, on the transmitting side, a plurality of laser modules 81 to 8n are arranged on the same Peltier element 110 constituting the temperature control element of the present invention via a module fixing plate 111 having good thermal conductivity.
The thermistor 11 is placed on the module fixing plate 111.
2 is provided to output the detected temperature to the ATC circuit 113. The ATC circuit 113 controls the temperature of the Peltier element 110 to keep the temperature of each of the laser modules 81 to 8n constant so that the temperature from the thermistor 112 is kept constant. Are kept constant. The light output from the plurality of laser modules 81 to 8n is an optical coupler or WD
The light is multiplexed by the M coupler 90 and transmitted to the multiplexed light transmission line 91 as wavelength multiplexed light.

On the receiving side, the passing wavelength is adjusted by the WDM filter 92, separated into light of different wavelengths, and the light of each wavelength is received by the photoelectric converters 101 to 10n. As described above, in the present embodiment, the plurality of laser modules 81 to 8 n are connected to the same Peltier device 1.
10 and the temperature of each laser is managed in a unified manner, so that the wavelength of each laser is kept constant and the WDM
Also in the filter 92, the wavelength of the light passing through the output unit is kept constant, so that a wavelength multiplexing optical communication system with little deterioration in transmission quality can be provided.

The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the optical filter unit in each of the embodiments outputs the passing light of the wavelength adjusting light and the reference light in the FBG unit, but may be configured to output the reflected light of these lights.

[0087]

As described above, according to the first aspect of the present invention,
In the optical filter section, a part of the light output from the optical device is output as a wavelength adjusting light by passing or reflecting, and the output level of the wavelength adjusting light changes in response to a change in the wavelength of the wavelength adjusting light. And an optical wavelength adjustment device having a wavelength adjustment unit that adjusts the wavelength of light output from the optical device so that the output level of the wavelength adjustment light output from the optical filter unit approaches a predetermined value, Since the FBG section provided with the wavelength fluctuation suppressing section is used in the optical filter section, the temperature dependence of the wavelength adjustment can be reduced.

According to a sixth aspect of the present invention, there is provided a light source having an automatic output control unit, wherein a part of the output light is used as wavelength adjusting light, and the optical filter unit and the wavelength adjusting unit are characterized.
Since the temperature of the optical device is controlled by the optical wavelength adjusting device, the oscillation wavelength fluctuation can be reduced with a simple configuration. According to a seventh aspect of the present invention, there is provided an input unit to which a wavelength multiplexed light obtained by multiplexing a plurality of wavelengths of light is input, and an output unit that separates the wavelength multiplexed light into a plurality of lights of predetermined wavelengths and outputs the lights. An optical wavelength separation device, wherein a part of light of any wavelength of light output from the output unit is used as wavelength adjustment light, and the optical filter unit and the wavelength adjustment unit are characterized. Since the wavelength of the light output from the optical wavelength demultiplexing device is adjusted by any one of the optical wavelength adjusting devices 1 to 5, the configuration is simple and the fluctuation of the passing wavelength can be reduced.

According to the present invention, a plurality of light sources for outputting lights having different wavelengths from each other, a multiplexed optical transmission line for transmitting wavelength multiplexed light obtained by multiplexing lights output from the plurality of light sources, 8. The optical wavelength separation device according to claim 7, wherein the wavelength multiplexed light transmitted through the optical transmission line is input, and is separated and output to light of different wavelengths, and the respective light output from the optical wavelength separation device is received. 6. The optical receiver according to claim 1, wherein each of the light sources uses a part of its own output light as wavelength adjusting light, and has a characteristic in an optical filter unit and a wavelength adjusting unit. Since the wavelength of the output light is adjusted by the optical wavelength adjusting device, deterioration of transmission quality can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a basic configuration of an optical wavelength adjustment device according to the present invention.

FIG. 2 is a cross-sectional view of the first embodiment showing a specific configuration of the wavelength fluctuation suppressing section shown in FIG.

FIG. 3 is a sectional view of a second embodiment.

FIG. 4 is a relationship diagram showing an example of a relationship between a temperature of an FBG portion and a change in Bragg wavelength.

FIG. 5 is a configuration diagram of a third embodiment showing a specific configuration of the wavelength fluctuation suppressing unit.

FIG. 6 is a configuration diagram showing a configuration in which two FBG units having different Bragg wavelengths are arranged in series.

FIG. 7 is a configuration diagram showing a configuration of a first embodiment of an optical wavelength adjusting apparatus for an optical device according to the present invention.

FIG. 8 is a configuration diagram illustrating a configuration of the laser module illustrated in FIG. 1;

FIG. 9 is a diagram for explaining transmission spectra of two FBG units.

FIG. 10 is a diagram illustrating a combined transmission spectrum of two FBG units.

FIG. 11 is a diagram showing a relationship between a voltage signal corresponding to light passing through an FBG unit and a wavelength.

FIG. 12 is a configuration diagram showing a configuration of a second embodiment of an optical wavelength adjusting apparatus for an optical device according to the present invention.

FIG. 13 is a configuration diagram showing the configuration of the third embodiment.

FIG. 14 is a top view illustrating a first example of a configuration of a wavelength fluctuation suppressing unit used in the present invention.

FIG. 15 is a side view of the same.

FIG. 16 is a top view showing a second example of the configuration of the wavelength fluctuation suppressing unit.

FIG. 17 is a top view showing a third example of the configuration of the wavelength fluctuation suppressing unit.

FIG. 18 is a side view of the same.

FIG. 19 is a top view showing a fourth example of the configuration of the wavelength fluctuation suppressing unit.

FIG. 20 is a top view showing a fifth example of the configuration of the wavelength fluctuation suppressing unit.

FIG. 21 shows first to third optical wavelength adjusting apparatuses according to the present invention.
FIG. 9 is a configuration diagram of another example of the configuration of the FBG unit shown in the embodiment.

FIG. 22 is a diagram for explaining the transmission spectrum of the grating in FIG. 21.

FIG. 23 is a configuration diagram showing the configuration of a fourth embodiment of the optical wavelength adjusting apparatus for an optical device according to the present invention.

FIG. 24 is a diagram for explaining a transmission spectrum of the FBG unit shown in FIG. 23;

FIG. 25 is a relationship diagram showing a relationship between an output voltage and a wavelength corresponding to light passing through the FBG unit.

FIG. 26 is a relationship diagram showing a relationship between a voltage signal from a voltage converter and a wavelength.

FIG. 27 is a configuration diagram showing the configuration of a fifth embodiment of the optical wavelength adjusting apparatus for an optical device according to the present invention.

FIG. 28 is a relationship diagram illustrating a relationship between the transmittance and the wavelength of the FBG unit illustrated in FIG. 27;

FIG. 29 is a relationship diagram showing a relationship between a difference voltage of the FBG unit and a wavelength.

FIG. 30 is a configuration diagram showing the configuration of a sixth embodiment of the optical wavelength adjusting apparatus for an optical device according to the present invention.

FIG. 31 is a characteristic diagram illustrating characteristics of a voltage signal and a wavelength from the differential amplifier illustrated in FIG. 30;

FIG. 32 is a configuration diagram showing a configuration of an optical wavelength adjusting apparatus for an optical device according to a seventh embodiment of the present invention.

FIG. 33 is a configuration diagram showing a configuration of an example of an optical wavelength separation device according to the present invention.

FIG. 34 is a configuration diagram showing a configuration of an example of a WDM optical communication system according to the present invention.

FIG. 35 is a configuration diagram showing a configuration of another example of the WDM optical communication system.

[Explanation of symbols]

Reference Signs List A Optical device 11, 67 Optical coupler 12 Optical filter unit 13 Wavelength fluctuation suppressing unit 14 Wavelength adjusting unit 15, 27, 28, 40, 41, 60, 68 FBG unit 15a, 27a, 28a, 61 Fiber grating 23, 42, 43 , 112 Thermistors 24, 36, 44, 45, 63, 110 Peltier devices 25, 34, 46, 47, 113 ATC circuits 30, 81 to 8n Laser modules 30a Lasers 31, 62 Fibers 32, 64 APC circuits 33, 37, 69 PD 34a, 34f Voltage converter 34b Monitor circuit 34c Reference voltage regulator 34d Differential amplifier 34e Peltier current control circuit 56,57 Piezoelectric element 58,59 DC voltage source 65 Modulator 70 Optical attenuator 71,92 WDM filter 72 Input waveguide 73 Output waveguide 74, 75 Slab waveguide 76 Array waveguide 77,78 Optical tap 79 1/2 wavelength plate 91 Multiplexed optical transmission line 101-10n Opto-electric converter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Omura 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Kazuo Kogure 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (9)

[Claims] 1. An optical device according to claim 1, wherein a part of the light output from the optical device is output as a wavelength adjusting light by passing or reflecting the light, and an output level of the wavelength adjusting light changes in response to a wavelength change of the wavelength adjusting light. An optical wavelength adjustment device comprising: an optical filter unit; and a wavelength adjustment unit that adjusts the wavelength of light output from the optical device such that the output level of the wavelength adjustment light output from the optical filter unit approaches a predetermined value. An optical wavelength adjusting device, wherein a fiber Bragg grating unit provided with a wavelength fluctuation suppressing unit is used for the optical filter unit. 2. The optical filter section, wherein two fiber Bragg grating sections having mutually different Bragg wavelengths are arranged in series, and the wavelength adjusting section adjusts the wavelength adjusting light output from the optical filter section. The optical wavelength adjusting apparatus according to claim 1, wherein the wavelength of the light output from the optical device is adjusted so that the output level approaches a peak value between the Bragg wavelengths of the two fiber Bragg grating sections. 3. The optical filter section is a resonator formed by arranging fiber Bragg grating sections in series, and the wavelength adjusting section includes an output level of wavelength adjusting light output from the optical filter section. 2. The optical wavelength adjusting apparatus according to claim 1, wherein the wavelength controller adjusts the wavelength of the light output from the optical device so as to approach a peak value corresponding to the Bragg wavelength of the fiber Bragg grating. 4. The optical filter section comprises one fiber Bragg grating section, and in the wavelength adjusting section, the output level of the wavelength adjusting light output from the optical filter section depends on the wavelength of the fiber Bragg grating section. The optical wavelength adjustment device according to claim 1, wherein the wavelength of the light output from the optical device is adjusted so as to approach a predetermined level in the sloping portion. 5. The optical filter unit according to claim 1, wherein one of the light branched from a part of the light output from the optical device is passed through a fiber Bragg grating unit having a predetermined Bragg wavelength as wavelength adjusting light. Reflected, and the other light is passed or reflected to a reference light passing portion as reference light, and is output.The output level of the wavelength adjusting light output from the fiber Bragg grating portion is output by the wavelength adjusting portion. And, using a voltage value based on a difference between the output level of the reference light output from the reference light passing unit as an adjustment voltage value, and adjusting the voltage value from the optical device such that the adjustment voltage value approaches a predetermined set voltage value. The optical wavelength adjustment device according to claim 1, wherein the wavelength of the output light is adjusted. 6. A light source having an automatic output control unit, wherein a part of output light is used as wavelength adjusting light.
Wherein the temperature of the optical device is controlled by the optical wavelength adjusting device. 7. An input unit to which a wavelength multiplexed light obtained by multiplexing a plurality of wavelengths of light is input, and an output unit that separates the wavelength multiplexed light into a plurality of lights of predetermined wavelengths and outputs the lights. The light wavelength separation device according to claim 1, wherein a part of light having any one of wavelengths output from the output unit is used as wavelength adjustment light, and
Wherein the wavelength of light output from the optical wavelength separation device is adjusted by any one of the optical wavelength adjustment devices. 8. A plurality of light sources for outputting light having different wavelengths from each other, a multiplexed light transmission line for transmitting wavelength multiplexed light obtained by multiplexing light output from the plurality of light sources, and the multiplexed light transmission line. 8. The optical wavelength separation device according to claim 7, wherein the wavelength-division multiplexed light transmitted through the optical wavelength separation device is input and separated into light beams having different wavelengths, and the light reception device receives the respective light beams output from the optical wavelength separation device. Each light source uses a part of its own output light as wavelength adjusting light, and the wavelength of the output light is adjusted by the optical wavelength adjusting device according to any one of claims 1 to 5. Wavelength multiplexing optical communication system. 9. A plurality of light sources for outputting light having different wavelengths from each other, a multiplexed light transmission line for transmitting a wavelength multiplexed light obtained by multiplexing lights output from the plurality of light sources, and the multiplexed light transmission line 8. The optical wavelength separation device according to claim 7, wherein the wavelength-division multiplexed light transmitted through the optical wavelength separation device is input and separated into light beams having different wavelengths, and the light reception device receives the respective light beams output from the optical wavelength separation device. A plurality of light sources are arranged on the same temperature control element,
A wavelength division multiplexing optical communication system, wherein the temperatures of the plurality of light sources are centrally managed.