JP2008172717A - Wavelength control circuit and wavelength multiplex optical transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength control circuit and a wavelength multiplex optical transmission apparatus which can stabilize a plurality of wavelengths by economical method. <P>SOLUTION: The wavelength multiplex optical transmission apparatus 100 is provided with N sets of optical transmitters 102-1 to 102-N with different transmission wavelengths, a wavelength multiplexer 104 for multiplexing an optical signal from the optical transmitter, an optical coupler 106 for branching a multiplexed optical signal, a photodetector 108 for receiving an optical signal from the optical coupler, and a wavelength control means 110 for controlling wavelength of each optical transmitter based on a signal from the photodetector. The wavelength multiplexer 104 has periodic spectral characteristics. The wavelength control means 110 controls one of N sets of optical transmitters so as to maximize the value of optical power from the photodetector. When N sets of optical transmitters are controlled one by one sequentially, all transmission wavelengths coincide with the peak of periodic spectral characteristics of the wavelength multiplexer. Thereby, all transmission wavelengths of optical transmitters can be stabilized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength control circuit and a wavelength division multiplexing optical transmission apparatus in a wavelength division multiplexing optical communication system.

  In a wavelength division multiplexing optical communication system, a plurality of optical signals having different wavelengths are transmitted by a single optical fiber cable. A plurality of optical signals having different wavelengths are multiplexed / demultiplexed by using a multiplexer / demultiplexer such as a dielectric multilayer filter or an arrayed waveguide diffraction grating. In many cases, the transmission center wavelengths of the wavelength multiplexer are set at equal intervals to the wavelength determined by ITU-T.

  In this wavelength division multiplexing optical communication system, when a certain signal wavelength drifts from a predetermined wavelength, not only the optical power of the signal wavelength itself is attenuated but also crosstalk to adjacent wavelengths. Stabilizing the signal wavelength is particularly important in a high-density wavelength division multiplexing optical transmission system.

  FIG. 1 shows an example of a wavelength division multiplexing optical transmission apparatus in a conventional wavelength division multiplexing optical communication system (see Non-Patent Document 1). The wavelength division multiplexing optical transmission apparatus 10 combines optical signals having different wavelengths from N optical transmitters 12-1 to 12 -N with a wavelength multiplexer 14 and through a single optical fiber cable (not shown). To transmit. The optical transmitters 12-1 to 12 -N perform wavelength stabilization through the optical filters 16-1 to 16 -N and the light receivers 18-1 to 18 -N, respectively. That is, the optical signal from the optical transmitter is monitored by the optical receiver through the optical filter having a predetermined wavelength transmission characteristic, and the wavelength of the optical transmitter is controlled based on the result. Can be stabilized. In this way, the spectral characteristics of the optical filter are used as a wavelength reference, and wavelength stabilization is realized.

  An inexpensive etalon filter or the like is used as the optical filter. The etalon filter has a reflective coat formed on both ends of a parallel plate, and a periodic input / output characteristic as shown in FIG. 2 is obtained by multiple reflection between the reflective coats. By setting the natural number times the FSR of the etalon filter to be equal to the transmission center wavelength interval of the wavelength multiplexer 14, it can be used as a wavelength reference in the wavelength division multiplexing optical transmitter 10. That is, when the transmission wavelength from the optical transmitter changes from the target wavelength reference, the output optical power of the optical filter changes depending on the characteristics of the optical filter. The wavelength can be controlled to the target wavelength reference.

  FIG. 3 shows an example of another wavelength division multiplexing optical transmission apparatus in a conventional wavelength division multiplexing optical communication system (see Patent Document 1). This wavelength division multiplexing optical transmission apparatus 20 combines optical signals having different wavelengths from N optical transmitters 12-1 to 12 -N with a wavelength multiplexer 24 and transmits it through a single optical fiber cable. The combined optical signal is branched by the optical coupler 26, demultiplexed by the wavelength demultiplexer 34 via the Mach-Zehnder filter 28, and the optical power is monitored by the light receivers 32-1 to N.

  FIG. 4 shows the transmission spectrum characteristics of the Mach-Zehnder filter. The Mach-Zehnder filter 28 can be used as a wavelength reference in the wavelength division multiplexing optical transmitter 20 by setting the natural number multiple of the FSR to be equal to the transmission center wavelength interval of the wavelength demultiplexer 34 as in the etalon filter. . The transmission center wavelength of this Mach-Zehnder filter is perturbed by an oscillator 30, and output signals from the light receivers 32-1 to N are synchronously detected by multipliers 36-1 to 36-N, and a low-pass filter (LPF) 38-1 to 38-1 The transmission wavelength of the optical transmitter can be stabilized by controlling the transmission wavelength of the optical transmitter so that the output of N becomes zero.

JP-A-9-261181 “A Highly Stable and Reliable Wavelength Monitor Integrated Laser Module Design,” J. Lightwave Technol., Vol.22, pp1344-1351, May 2004

  However, since the wavelength division multiplexing optical transmitter of FIG. 1 performs wavelength stabilization separately for each optical transmitter, an optical filter and a light receiver are required for each optical transmitter, and the cost is proportional to the number of optical transmitters. There was a problem that became high.

  Further, in the wavelength division multiplexing optical transmission apparatus of FIG. 3, the functions of N optical filters can be realized by one Mach-Zehnder filter and wavelength demultiplexer, compared with the configuration of FIG. The device is relatively expensive and requires not only a light receiver but also a multiplier and an LPF. Furthermore, this configuration has a problem that the initial introduction cost is high because a wavelength demultiplexer corresponding to the maximum number of wavelengths used in the system must be prepared in advance regardless of the number of wavelengths in operation. .

  The present invention has been made in view of such problems, and it is an object of the present invention to provide a wavelength control circuit and a wavelength division multiplexing optical transmission apparatus that can stabilize a plurality of wavelengths in an economical manner.

  In order to achieve the above object, the present invention provides a wavelength control circuit according to claim 1, comprising: an optical transmission means capable of changing each of a plurality of transmission wavelengths; and the plurality of transmission wavelengths. In contrast, with respect to a plurality of transmission wavelengths of the optical transmission means, an optical filter means for providing a spectral characteristic serving as a reference, a light receiving means for receiving light of the plurality of transmission wavelengths via the optical filter means, Wavelength control means for sequentially controlling each transmission wavelength based on the optical power obtained by the light receiver is provided.

  The invention according to claim 2 is the wavelength control circuit according to claim 1, wherein the optical filter means gives a maximum peak of optical power to each transmission wavelength as a reference spectral characteristic. The wavelength control unit sequentially controls each transmission wavelength with respect to a plurality of transmission wavelengths of the optical transmission unit on the basis of the maximum value of the optical power obtained by the light receiver.

  The invention according to claim 3 is the wavelength control circuit according to claim 1, wherein the optical filter means gives a minimum peak of optical power to each transmission wavelength as a reference spectral characteristic. The wavelength control means sequentially controls each transmission wavelength for a plurality of transmission wavelengths of the optical transmission means with reference to a minimum value of optical power obtained by the light receiver.

  According to a fourth aspect of the present invention, there is provided a wavelength control circuit comprising: an optical transmission means capable of changing each of a plurality of transmission wavelengths; and a light that gives a reference spectral characteristic to the plurality of transmission wavelengths. Filter means, wherein the first output port and the second output port have reverse spectral characteristics, and the first output port receives light of the plurality of transmission wavelengths via the first output port. A first light receiving means, a second light receiving means for receiving light of the plurality of transmission wavelengths via the second output port, and a plurality of transmission wavelengths of the light transmission means. And a wavelength control means for sequentially controlling each transmission wavelength on the basis of the optical power obtained by the photoreceiver.

  The invention according to claim 5 is the wavelength control circuit according to claim 4, wherein the wavelength control means is obtained by the first light receiver for a plurality of transmission wavelengths of the optical transmission means. Each transmission wavelength is sequentially controlled on the basis of the difference between the optical power and the optical power obtained by the second light receiver.

  The invention according to claim 6 is the wavelength control circuit according to claim 4, wherein the optical filter means has a first spectral characteristic as a reference spectral characteristic for each transmission wavelength. A maximum peak of optical power is given, and a minimum peak of optical power is given to each wavelength at the second output port. Each transmission wavelength is sequentially controlled on the basis of the maximum value of the optical power obtained by one light receiver, and the light obtained by the second light receiver for a part of the plurality of transmission wavelengths of the optical transmission means. Each transmission wavelength is sequentially controlled based on the minimum power value.

  The invention according to claim 7 is the wavelength control circuit according to claim 6, wherein the wavelength control unit further includes the first light receiving unit for a part of a plurality of transmission wavelengths of the optical transmission unit. Each transmission wavelength is sequentially controlled based on the difference between the optical power obtained by the optical device and the optical power obtained by the second light receiver.

  The invention according to claim 8 is the wavelength control circuit according to any one of claims 1 to 7, wherein the optical filter means has a spectral characteristic for waveform shaping for each transmission wavelength. Furthermore, it is characterized by giving.

  The invention according to claim 9 is the wavelength control circuit according to any one of claims 1 to 8, wherein the optical filter means includes an optical filter having a periodic spectral characteristic, a wavelength multiplexer, Or it is the combination of these.

  The invention according to claim 10 is the wavelength control circuit according to any one of claims 1 to 8, wherein the optical filter means is an etalon filter, a Mach-Zehnder filter, or a combination thereof. And

  The invention described in claim 11 is a wavelength division multiplexing optical transmitter, comprising the wavelength control circuit according to any one of claims 1 to 10.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 5 shows an example of a wavelength division multiplexing optical transmission apparatus according to the first embodiment of the present invention. This wavelength division multiplexing optical transmitter 100 includes N optical transmitters 102-1 to N having different transmission wavelengths, a wavelength multiplexer 104 that combines optical signals from the optical transmitters, and the combined optical signal. A branching optical coupler 106, a light receiver 108 for receiving an optical signal from the optical coupler, and a wavelength control means 110 for controlling the wavelength of each optical transmitter based on the signal from the light receiver are provided. The wavelength control unit 110 can individually control the transmission wavelengths of the N optical transmitters 102-1 to 102-N.

  The case where an arrayed waveguide grating having a Gaussian transmission characteristic is used as the wavelength multiplexer 104 will be described as an example. As shown in FIG. 6, the wavelength multiplexer 104 has the maximum transmittance at the transmission center wavelength. Therefore, when all the transmission wavelengths of the optical transmitters 102-1 to 102 -N coincide with the transmission center wavelength of the wavelength multiplexer 104, the optical power obtained by the light receiver 108 becomes maximum, and the transmission wavelength of the optical transmitter Is stabilized at the transmission center wavelength of the wavelength multiplexer.

  Here, how to determine the transmission wavelength of the optical transmitter is a problem as to whether all the transmission wavelengths of the optical transmitter match the transmission center wavelength of the wavelength multiplexer. In the configuration of FIG. 5, since the power of wavelength multiplexed light is received by a single light receiver 108, if the transmission wavelengths of a plurality of optical transmitters are changed at the same time, the change in optical power obtained by the light receivers is changed. Therefore, it cannot be determined which optical transmitter corresponds to the change in the transmission wavelength. Therefore, the wavelength control is performed by changing only the transmission wavelength of one optical transmitter and maximizing the optical power obtained by the light receiver. By performing this operation one by one for each optical transmitter, the transmission wavelengths of all the optical transmitters can be stabilized.

  This will be described with reference to FIG. For the i-th optical transmitter i (i = 1, 2,..., N), the transmission wavelength is continuously changed, and the wavelength at which the optical power obtained by the light receiver 108 is maximized is determined and held. Here, the range in which the transmission wavelength is changed can be determined based on the transmission characteristics of the wavelength multiplexer so that the transmission wavelength of the optical transmitter i is locked to the corresponding transmission center wavelength. For example, it is possible to set the range from the adjacent valley to the valley centered on the transmission center wavelength corresponding to the optical transmitter i. Next, for the (i + 1) th optical transmitter i + 1, the wavelength at which the optical power obtained by the light receiver 108 is maximized is determined and held. As described above, the search for the maximum value of the optical power received by the light receiver 108 is sequentially performed for the N optical transmitters, so that the transmission wavelengths of all the optical transmitters can be matched with the wavelength multiplexer 104 respectively. The transmission center wavelength can be stabilized. This stabilization may be performed at any time. By performing this sequential maximum value search control, every time a new optical transmitter is added, it is only necessary to stabilize the transmission wavelength of the optical transmitter, and the components necessary for wavelength control can be shared by all optical transmitters. Thus, it is possible to configure a wavelength division multiplexing optical transmission apparatus with reduced initial cost.

  Here, as the maximum value search method, the method of searching for the maximum value by continuously changing the wavelength has been described, but the wavelength that becomes the maximum value by fitting from the hill-climbing method or several discrete measurement points An arbitrary maximum value search method such as a method for determining the value can be adopted. The same applies to other embodiments.

(Second Embodiment)
FIG. 8 shows an example of a wavelength division multiplexing optical transmission apparatus according to the second embodiment of the present invention. In this wavelength division multiplexing optical transmission apparatus 200, an optical filter 202 is inserted before the light receiver 108 of the wavelength division multiplexing optical transmission apparatus 100 according to the first embodiment. The optical filter 202 has a characteristic that the natural number multiple of the FSR is equal to the transmission center wavelength interval of the wavelength multiplexer 104, and the maximum output power is obtained at the transmission center wavelength of the wavelength multiplexer. Examples of such an optical filter include an etalon filter having transmission characteristics as shown in FIG. 2 and a Mach-Zehnder filter having transmission characteristics as shown in FIG.

  When the wavelength multiplexer / demultiplexer 104 having a flat transmission characteristic as shown in FIG. 9 is used, it is impossible to uniquely determine the wavelength at which the transmittance is maximum. At this time, by using the optical filter 202 having the characteristics as described above and using the wavelength reference of the optical transmitter, the wavelength control unit 210 controls the transmission wavelength of the optical transmitter in the same manner as in the first embodiment. Stabilization can be performed.

  In addition, when the wavelength multiplexer 104 having Gaussian spectral characteristics is used, it is used for communication by setting the pass band of the optical filter 202 to be narrower than the transmission band of the wavelength multiplexer. The maximum value search control can be performed without greatly affecting the wavelength. Such a thing can be easily realized by setting the reflectance of the reflective coat to be high for an etalon filter, for example.

(Third embodiment)
FIG. 10 shows an example of a wavelength division multiplexing optical transmission apparatus according to the third embodiment of the present invention. In this wavelength division multiplexing optical transmission apparatus 300, the optical filter arranged in the previous stage of the light receiver 108 in the wavelength division multiplexing optical transmission apparatus 200 according to the second embodiment is arranged in the subsequent stage of the wavelength multiplexer 104. In this case, the optical filter 302 is used for wavelength stabilization and also for shaping the wavelength spectrum of the signal light used for communication.

  This will be described with reference to FIG. When directly modulated laser diodes (LD) are used as the optical transmitters 102-1 to 102-N, the transmitted light spectrum has two spectral peaks corresponding to the mark and space levels, respectively, due to its chirp characteristics, and the power difference between them. Corresponds to the extinction ratio. Here, since the optical power corresponding to the mark level is dominant with respect to the optical power of the transmission wavelength of a certain optical transmitter, when performing wavelength stabilization control by sequential maximum value search control in the wavelength control unit 310, The spectral peak wavelength corresponding to the mark level is stabilized at a predetermined wavelength. In this case, the spectral peak corresponding to the space level is filtered through the transmission characteristic of the optical filter 308 and suffers loss, and as a result, the extinction ratio increases. In the present embodiment, the single optical filter 308 can be used to simultaneously stabilize the transmission wavelengths and waveform shaping of the N optical transmitters.

(Fourth embodiment)
FIG. 12 shows an example of a wavelength division multiplexing optical transmission apparatus according to the fourth embodiment of the present invention. The wavelength division multiplexing optical transmission apparatus 400 has the same configuration as the wavelength division multiplexing optical transmission apparatus 200 according to the second embodiment, but here, an optical filter 402 having different characteristics from the optical filter 202 is used. In this optical filter 402, as shown in FIG. 13, the natural number multiple of the FSR is equal to the transmission center wavelength interval of the wavelength multiplexer 104, and the input power at which the minimum output power can be obtained at the transmission center wavelength of the wavelength multiplexer is obtained. Has output characteristics.

  The optical filter 402 having such characteristics can be obtained by observing the reflected output of the etalon filter as shown in FIG. In order to observe the reflected output, as shown in FIG. 14A, light is obliquely incident on the etalon filter and the reflected light is observed. Alternatively, as shown in FIG. 14B, there is a method in which light is incident perpendicularly to the etalon filter and the reflected output is extracted using the circulator 50.

  The optical filter 402 having such characteristics can also be obtained by setting the point where the transmittance of the Mach-Zehnder filter is minimum as the transmission center wavelength of the wavelength multiplexer 104, as shown in FIG.

  Using the optical filter 402 having such input / output characteristics, as shown in FIG. 16, the wavelength control is performed so that the optical power obtained by the light receiver 108 is minimized for each of the optical transmitters 102-1 to 102-N. By performing the minimum value search control one by one in the means 410, the transmission wavelengths of all the optical transmitters can be stabilized at the transmission center wavelength of the wavelength multiplexer 104.

  In a configuration in which sequential maximum value search control is performed, the total transmission wavelength is stabilized by searching for the maximum value of optical power for each optical transmitter. However, when performing wavelength stabilization of a plurality of optical transmitters whose wavelengths are not stabilized, the transmission wavelength change of the optical transmitter with respect to the total light reception power is the more the optical transmitter whose wavelength is stabilized first. The ratio of the change in the received light power is large, and the ratio is smaller as the optical transmitter whose wavelength is stabilized later. This means that the effect of noise due to an accidental change in optical power other than the wavelength to be stabilized increases as the optical transmitter that performs maximum value search control later increases, and the accuracy of wavelength stabilization decreases.

  In the present embodiment, contrary to the second embodiment, the ratio of the received light power change accompanying the change in the transmission wavelength of the optical transmitter with respect to the total received power is smaller for the optical transmitter whose wavelength is stabilized first. The ratio of the optical transmitter whose wavelength is stabilized later is larger. When optical transmitters are added gradually, the wavelength of the optical transmitter that has been operating before the addition has already been stabilized, so that the sequential maximum value is determined by using the sequential minimum value search control of this embodiment. The maximum number of applicable optical transmitters can be increased as compared with the configuration in which search control is performed.

(Fifth embodiment)
FIG. 17 shows an example of a wavelength division multiplexing optical transmission apparatus according to the fifth embodiment of the present invention. In this wavelength division multiplexing optical transmission apparatus 500, an optical filter 502 is used instead of the optical coupler 106 of the wavelength division multiplexing optical transmission apparatus 100 according to the first embodiment. In this optical filter 502, a natural number multiple of its FSR is equal to the transmission center wavelength interval of the wavelength multiplexer 104, its output port 1 is used for communication, and its output port 2 is used for wavelength stabilization. . For the output port 1, as shown in FIG. 2, the maximum optical power is obtained at the transmission center wavelength of the wavelength multiplexer 104, and for the output port 2, as shown in FIG. The input / output characteristics are such that the minimum optical power is obtained at the transmission center wavelength.

  The optical filter 502 having such characteristics can be obtained by using the transmission output of the etalon filter as port 1 and the reflection output as port 2 as shown in FIGS. Further, as shown in FIG. 18 (c), the port in which the transmission center wavelength of the Mach-Zehnder filter is set to be the maximum at the transmission center wavelength of the wavelength multiplexer 104 is designated as port 1, and the other port is designated as port 2. Also good. With such a configuration, the waveform shaping described in the third embodiment and the wavelength stabilization by the sequential minimum value search control described in the fourth embodiment can be performed simultaneously.

(Sixth embodiment)
FIG. 19 shows an example of a wavelength division multiplexing optical transmitter according to the sixth embodiment of the present invention. In the wavelength division multiplexing optical transmission apparatus 600, the optical filter of the wavelength division multiplexing optical transmission apparatus 500 according to the fifth embodiment is arranged at the subsequent stage of the optical coupler 106. In this case, the wavelength control unit 610 sequentially performs maximum value search control on the light receiver 604 and sequentially performs minimum value search control on the light receiver 606, so that N optical transmitters 102-1 to N-1 are obtained. The transmission wavelength can be stabilized.

  As explained in the fourth embodiment, the wavelength stabilization accuracy is higher in the optical transmitter controlled earlier in the sequential maximum value search control, and conversely, the wavelength is higher in the optical transmitter controlled later in the sequential minimum value search control. Stabilization accuracy is high. Therefore, in the present embodiment, a configuration in which only one control is performed by performing sequential maximum value search control in an optical transmitter that is controlled first and performing sequential minimum value search control in an optical transmitter that is controlled later. The maximum number of applicable optical transmitters can be increased.

(Seventh embodiment)
FIG. 20 shows an example of a wavelength division multiplexing optical transmission apparatus according to the seventh embodiment of the present invention. This wavelength division multiplexing optical transmission apparatus 700 has the same configuration as the wavelength division multiplexing optical transmission apparatus of the sixth embodiment. In the present embodiment, the wavelength control means 710 subtracts the value of the optical power obtained by the light receiver 706 from the value of the optical power obtained by the light receiver 704, and sequentially performs maximum value search control on the value. The subtraction may be performed by electrically subtracting the output of the optical receiver or by subtracting the optical power received by the optical receivers 704 and 706 once numerically.

  This embodiment will be described with reference to FIG. As shown in the figure, by subtracting the optical power value obtained by the optical receiver 706 from the optical power value obtained by the optical receiver 704, the amount of change in optical power is twice that when only one optical receiver is used. It becomes. Therefore, the maximum number of applicable optical transmitters can be increased as compared with the configuration using only one light receiver.

(Eighth embodiment)
FIG. 22 shows an example of a wavelength division multiplexing optical transmission apparatus according to the eighth embodiment of the present invention. The wavelength division multiplexing optical transmission apparatus 800 is configured by combining the wavelength division multiplexing optical transmission apparatus 300 of the third embodiment with the wavelength division multiplexing optical transmission apparatus 500 of the fifth embodiment. With such a configuration, the waveform shaping described in the third embodiment and the wavelength stabilization described in the sixth embodiment can be performed simultaneously. Specifically, sequential maximum value search control can be performed on the light receiver 804, and sequential minimum value search control can be performed on the light receiver 806.

(Ninth embodiment)
FIG. 23 shows an example of a wavelength division multiplexing optical transmitter according to the ninth embodiment of the present invention. This wavelength division multiplexing optical transmission apparatus 900 has the same configuration as the wavelength division multiplexing optical transmission apparatus 800 of the eighth embodiment. In the present embodiment, the wavelength shaping described in the third embodiment and the wavelength stabilization described in the seventh embodiment can be performed simultaneously. Specifically, the maximum value search control can be sequentially performed on a value obtained by subtracting the optical power value obtained by the light receiver 906 from the optical power value obtained by the light receiver 904.

(Other embodiments)
In the sixth to ninth embodiments, both the optical powers of the output port 1 and the output port 2 of the optical filter 502 described in the fifth embodiment are monitored. In this case, the value obtained by adding the loss from the output end of the optical multiplexer to the optical receiver 1 to the optical power value obtained by the optical receiver 1 and the optical power output obtained by the optical receiver 2 are output. The total optical power of the wavelength multiplexed light can be estimated in consideration of the branching ratio of the optical coupler 106 by performing addition with a value obtained by adding the loss from the end to the light receiver 2. In this way, the total optical power of the wavelength multiplexed light used for communication can be obtained without adding a new light receiver, which can be used for management operation of the wavelength multiplexed optical communication system.

  While the present invention has been described with respect to several specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied. It is not intended to limit the scope of the invention. For example, an array waveguide diffraction grating, an etalon filter, and a Mach-Zehnder filter have been described as examples of optical filter means for providing a reference spectral characteristic, but a ring resonator filter, a Fabry-Perot interference fiber Bragg grating filter is used. Also good. Therefore, the configuration and details of the embodiment exemplified herein can be changed without departing from the spirit of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

It is a figure which shows an example of the wavelength division multiplexing optical transmitter in the conventional wavelength division multiplexing optical communication system. It is a figure which shows an example of the spectrum characteristic of the optical filter of FIG. It is a figure which shows an example of another wavelength division multiplexing optical transmitter in the conventional wavelength division multiplexing optical communication system. It is a figure which shows an example of the spectrum characteristic of the Mach-Zehnder filter of FIG. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 1st Embodiment of this invention. It is a figure which shows an example of the spectrum characteristic of the wavelength multiplexer of FIG. It is a figure for demonstrating the sequential maximum value search control in the wavelength control means of this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 2nd Embodiment of this invention. It is a figure which shows an example of the spectrum characteristic of the wavelength multiplexer of FIG. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 3rd Embodiment of this invention. It is a figure for demonstrating stabilization of the transmission wavelength and waveform shaping of the optical transmitter by this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmitter by the 4th Embodiment of this invention. It is a figure which shows an example of the spectrum characteristic of the optical filter of FIG. FIG. 14A is a diagram illustrating a configuration example of the optical filter of FIG. 12, FIG. 14A is a configuration in which light is incident obliquely on the etalon filter, and FIG. 14B is a diagram in which light is perpendicular to the etalon filter. The incident light is extracted and the reflected output is extracted using the circulator 50. It is a figure which shows an example of the spectrum characteristic at the time of using a Mach-Zehnder filter for the optical filter of FIG. It is a figure for demonstrating the sequential minimum value search control in the wavelength control means of this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 5th Embodiment of this invention. FIG. 18A is a diagram illustrating a configuration example of the optical filter in FIG. 17. FIG. 18A illustrates a configuration using an etalon filter, FIG. 18B illustrates a configuration using an etalon filter and a circulator, and FIG. ) Is a configuration using a Mach-Zehnder filter. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 6th Embodiment of this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmitter by the 7th Embodiment of this invention. It is a figure for demonstrating the sequential maximum value search control with respect to the difference of the optical power of two light receivers in the wavelength control means of this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmission apparatus by the 8th Embodiment of this invention. It is a figure which shows an example of the wavelength division multiplexing optical transmitter by the 9th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 Wavelength multiplexing optical transmitter 30 Oscillator 34 Wavelength demultiplexer 36-1 to N Multiplier 50 Circulator 100 Wavelength multiplexed optical transmitter 200 according to the first embodiment 200 Wavelength multiplexed optical transmitter 300 according to the second embodiment 300 WDM optical transmitter 400 according to the third embodiment 400 WDM optical transmitter according to the fourth embodiment 500 WDM optical transmitter according to the fifth embodiment 600 WDM optical transmitter 700 according to the sixth embodiment 700 Wavelength division multiplexing optical transmission apparatus 800 according to the embodiment 800 Wavelength division multiplexing optical transmission apparatus according to the eighth embodiment 900 Wavelength division multiplexing optical transmission apparatus according to the ninth embodiment

Claims (11)

An optical transmission means capable of varying each of a plurality of transmission wavelengths;
Optical filter means for providing a reference spectral characteristic for the plurality of transmission wavelengths;
A light receiving means for receiving light of the plurality of transmission wavelengths via the optical filter means;
A wavelength control circuit comprising: wavelength control means for sequentially controlling each transmission wavelength with respect to a plurality of transmission wavelengths of the optical transmission means based on the optical power obtained by the light receiver. The wavelength control circuit according to claim 1,
The optical filter means gives a maximum peak of optical power for each transmission wavelength as a reference spectral characteristic,
The wavelength control circuit, wherein the wavelength control means sequentially controls each transmission wavelength for a plurality of transmission wavelengths of the optical transmission means with reference to a maximum value of optical power obtained by the light receiver. The wavelength control circuit according to claim 1,
The optical filter means gives a minimum peak of optical power for each transmission wavelength as a reference spectral characteristic,
The wavelength control circuit, wherein the wavelength control means sequentially controls each transmission wavelength for a plurality of transmission wavelengths of the optical transmission means with reference to a minimum value of optical power obtained by the light receiver. An optical transmission means capable of varying each of a plurality of transmission wavelengths;
Optical filter means for providing a reference spectral characteristic for the plurality of transmission wavelengths, wherein the first output port and the second output port have opposite spectral characteristics;
First light receiving means for receiving light of the plurality of transmission wavelengths via the first output port;
Second light receiving means for receiving the light of the plurality of transmission wavelengths via the second output port;
Wavelength control means for sequentially controlling each of the transmission wavelengths with respect to a plurality of transmission wavelengths of the optical transmission means on the basis of optical power obtained by the first and second optical receivers. Wavelength control circuit. The wavelength control circuit according to claim 4,
The wavelength control means, for a plurality of transmission wavelengths of the optical transmission means, each transmission wavelength based on the difference between the optical power obtained by the first light receiver and the optical power obtained by the second light receiver. A wavelength control circuit characterized by sequentially controlling. The wavelength control circuit according to claim 4,
The optical filter means gives a maximum optical power peak for each transmission wavelength to the first output port as a reference spectral characteristic, and a minimum optical power for each wavelength to the second output port. Give a peak,
The wavelength control unit sequentially controls each transmission wavelength with respect to a part of the plurality of transmission wavelengths of the optical transmission unit on the basis of the maximum value of the optical power obtained by the first light receiver. A wavelength control circuit for sequentially controlling each transmission wavelength with respect to a part of a plurality of transmission wavelengths of the transmission means on the basis of a minimum value of optical power obtained by the second light receiver. The wavelength control circuit according to claim 6,
The wavelength control means is further configured based on a difference between the optical power obtained by the first light receiver and the optical power obtained by the second light receiver for a part of the plurality of transmission wavelengths of the optical transmission means. A wavelength control circuit that sequentially controls each transmission wavelength. A wavelength control circuit according to any one of claims 1 to 7,
The wavelength control circuit, wherein the optical filter means further gives a spectral characteristic for waveform shaping to each transmission wavelength. A wavelength control circuit according to any one of claims 1 to 8,
The wavelength control circuit, wherein the optical filter means is an optical filter having a periodic spectral characteristic, a wavelength multiplexer, or a combination thereof. A wavelength control circuit according to any one of claims 1 to 8,
The wavelength control circuit, wherein the optical filter means is an etalon filter, a Mach-Zehnder filter, or a combination thereof.   A wavelength division multiplexing optical transmission apparatus comprising the wavelength control circuit according to claim 1.

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