JP2014078918A - Wavelength variable type optical transmission module and wavelength selection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength variable type optical transmission module capable of highly precisely achieving laser beams with inexpensive and optional wavelengths without using DFB laser or Peltier element.SOLUTION: The wavelength variable type optical transmission module 10 includes: a light-emitting device 11 that is Fabry-Perot semiconductor laser; a plurality of band-pass filters 12a-d that pass only the light of a specific wavelength from laser beams output by the light-emitting device 11, and an optical switch 13 that determines which of the band-pass filters permits laser beams output from the light-emitting device to pass through for switching according to a switching input from the outside.

Description

  The present invention relates to a wavelength tunable optical transmission module and a wavelength selection method, and more particularly to a wavelength tunable optical transmission module capable of selecting an arbitrary transmission light wavelength.

  As a semiconductor laser light emitting element used for optical communication, two types of systems such as a DFB (Distributed-Feedback) laser and an FP (Fabry-Perot) laser are mainly used. Since the DFB laser can oscillate only one wavelength stably, it is suitable for high-speed communication. However, since it is necessary to form a concavo-convex diffraction grating in the active layer, the manufacturing cost is high. On the other hand, the FP laser has a plurality of oscillation wavelengths because the active layer is simply constituted by the cleavage plane of the semiconductor crystal, and is not suitable for high-speed communication, but can be manufactured at a low cost (from Non-Patent Document 1). .

  FIG. 6 is an explanatory diagram schematically showing optical spectra of a general FP laser and a DFB laser. 6A shows the FP laser, and FIG. 6B shows the DFB laser. The DFB laser has a strong oscillation only at a single oscillation wavelength λ, whereas a plurality of oscillation wavelengths λ1, λ2, λ3.

  In recent years, the amount of data transmitted by data communication is increasing. In particular, so-called rich contents including high-quality video and high-quality sound are often distributed via the Internet. Therefore, WDM (Wavelength Division Multiplexing), which is a communication method for transmitting a plurality of optical signals having different wavelengths through one optical fiber, is generally used in an optical communication network.

  In WDM communication, semiconductor laser light sources that oscillate at different wavelengths are required. If all of these are to be covered by a conventional laser light source that oscillates only at a single frequency, it is necessary to prepare a separate light source for each frequency used in the communication. This is not realistic because the cost for maintaining the communication system becomes enormous. Therefore, the use of wavelength tunable lasers that can arbitrarily change the oscillation wavelength with a single laser light source is expanding. In this way, even if a light source of any wavelength becomes unavailable, it is possible to immediately replace the light source and continue communication.

  As the wavelength tunable laser, methods such as a semiconductor integrated type and a MEMS (Micro Electro Mechanical Systems) type are mainly used. A semiconductor integrated wavelength tunable laser changes the oscillation wavelength by changing the refractive index of an optical waveguide having a diffraction grating by current or electroheating. The MEMS type wavelength tunable laser changes the oscillation wavelength by mechanically rotating a diffraction grating attached to the outside of the light emitting unit (from Non-Patent Document 2).

  FIG. 7 shows the existing wavelength tunable conforming to OIF-ITLA-MSA (Multi-Source Agreement) which is a standard for ITLA (Integrable Tunable Laser Assembly) formulated by OIF (Optical Internetworking Forum). It is explanatory drawing shown about an example of a structure of the type | mold optical transmission module 910 (from nonpatent literature 3).

  The wavelength tunable optical transmission module 910 includes a DFB laser array 911 in which 12 DFB laser light emitting elements are coupled by an optical coupler, and an SOA (Semiconductor Optical) that amplifies the laser light output from the DFB laser array 911 and outputs the amplified laser light to the outside. Amplifier 912, a first photodiode 913 that monitors the intensity of the laser light output from the SOA 912, and an etalon filter 914a that extracts light of a specific wavelength component from the laser light output from the SOA 912. And a second photodiode 914b for detecting a wavelength shift of the light extracted by the etalon filter 914a.

  Since the etalon filter 914a and the second photodiode 914b have a function of suppressing wavelength fluctuation, they are collectively referred to as a wavelength locker 914. Each of the DFB laser array 911 and the etalon filter 914a is provided with Peltier elements 916a and 916b for cooling each. The Peltier elements 916a and 916b are also called TEC (Thermoelectrical Cooler).

  A control device 917 including a microprocessor controls the operations of the DFB laser array 911, the SOA 912, and the Peltier elements 916a and 916b based on the outputs from the first and second photodiodes 913 and 914b. . This wavelength tunable optical transmission module 910 is provided with an independently controllable Peltier element 916a and 916b in each of the DFB laser array 911 and the etalon filter 914a, so that the oscillation wavelength required in the OIF-ITLA-MSA is obtained. Realize the stability.

  In this connection, there are the following technical documents. Patent Document 1 describes a semiconductor laser module in which an FP laser is heated with a heater to stabilize the temperature. Patent Document 2 describes a single-wavelength optical oscillator that combines an FP laser and a bandpass filter to reduce the effect of temperature changes. Patent Document 3 describes a technique for minimizing the power consumption of an FP laser using a thermoelectric cooling element. Patent Document 4 describes a light modulation technique in a BLS (broadband light source) configured by mutual injection of two FP lasers.

  Non-Patent Document 1 describes the differences and features of each method of DFB laser and FP laser. Non-Patent Document 2 describes an outline of a general wavelength tunable laser. Non-Patent Document 3 describes an example of an existing wavelength tunable optical transmission module 910.

JP 2001-094200 A JP 2001-102684 A Special Table 2007-523493 Special table 2008-520124 gazette

Fujitsu Laboratories Ltd., "Semiconductor laser technology for optical communications" (from Easy Technology Course), [October 4, 2012 search], Fujitsu Laboratories Ltd., Internet <URL: http: // jp .fujitsu.com / group / labs / techinfo / techguide / list / laser_p06.html> Kazuo Enomoto et al., “Quick Learning Course, Optical Network (23)“ Wavelength Tunable Laser ”that Chooses Emission Wavelength” (from the main points of the network learned in one week), October 12, 2006, [October 2012 4 days search], Nikkei BP, Internet <URL: http://itpro.nikkeibp.co.jp/article/COLUMN/20061004/249885/> Koji Horikawa et al., “Development of ITLA with full-band tunable laser”, Furukawa Electric Time Report 123, February 2009, [October 4, 2012 search], Furukawa Electric Co., Ltd., Internet <URL : Http://www.furukawa.co.jp/jiho/fj123/fj123_02.pdf>

  The existing wavelength tunable optical transmission module represented by the optical transmission module 910 shown in FIG. 7 can obtain a laser beam having an arbitrary wavelength at a stable oscillation wavelength.

  However, in data communication, there is a constant demand for cost reduction and power saving as well as an increase in data capacity that can be transmitted. In that sense, the fact that existing optical transmission modules use “DFB laser” and “Peltier element (TEC)” as described above is a major obstacle to cost reduction and power saving. Yes. As described above, the DFB laser is more expensive than the FP laser, and the Peltier element (TEC) consumes a large amount of power.

  A technology that can solve this problem and realize a wavelength tunable optical transmission module that does not use a DFB laser or a Peltier element (TEC) is not described in the above-mentioned technical documents. Patent Documents 1 to 4 all describe FP lasers, but are not tunable lasers. Non-Patent Documents 1 to 3 all describe only the existing technology as described above.

  An object of the present invention is to provide a wavelength tunable optical transmission module and a wavelength selection method that can obtain a laser beam having an arbitrary wavelength with sufficient accuracy without using a DFB laser or a Peltier element (TEC). It is to provide.

  In order to achieve the above object, a wavelength tunable optical transmission module according to the present invention includes a light emitting element that is a Fabry-Perot semiconductor laser, and a plurality of light that passes only light having a specific wavelength different from laser light output from the light emitting element. And an optical switch for switching which band-pass filter the laser light output from the light-emitting element is passed through in accordance with an external switching input.

  In order to achieve the above object, a wavelength selection method according to the present invention operates a light emitting element that is a Fabry-Perot semiconductor laser to oscillate and output a laser beam, and the laser beam that is oscillated and output has a predetermined wavelength. The optical switch selects according to the external switching input whether to pass through different band pass filters that pass only the light of the selected light, and the selected band pass filter selectively outputs light of a specific wavelength from the laser light It was made to do.

  As described above, the present invention uses a Fabry-Perot type semiconductor laser and extracts light of a specific wavelength from the semiconductor laser using a bandpass filter, and thus does not use a DFB laser or a Peltier element. Thus, it is possible to provide a wavelength tunable optical transmission module and a wavelength selection method having an excellent feature that it is possible to obtain laser light having an arbitrary wavelength with sufficient accuracy at a low cost.

It is explanatory drawing shown about the structure of the wavelength variable type | mold optical transmission module which concerns on the 1st Embodiment of this invention. It is explanatory drawing shown about the optical spectrum of the laser beam which the light emitting element shown in FIG. 1 outputs. It is explanatory drawing shown about the optical spectrum of the laser beam which passed the band pass filter shown in FIG. FIG. 3A shows the case where the oscillation wavelength λ1 is selected by the optical switch, and FIG. 3B shows the case where the oscillation wavelength λ2 is selected. It is explanatory drawing shown about the structure of the wavelength-tunable optical transmission module which concerns on the 2nd Embodiment of this invention. It is explanatory drawing shown about the structure of the wavelength-tunable optical transmission module which concerns on the 3rd Embodiment of this invention. It is explanatory drawing which shows typically about the optical spectrum of a general FP laser and a DFB laser. 6A shows the FP laser, and FIG. 6B shows the DFB laser. It is explanatory drawing shown about an example of a structure of the existing wavelength-variable type | mold optical transmission module based on OIF-ITLA-MSA (Multi-Source Agreement).

(First embodiment)
Hereinafter, the structure of the 1st Embodiment of this invention is demonstrated based on attached FIG.
First, the basic content of the present embodiment will be described, and then more specific content will be described.
The wavelength tunable optical transmission module 10 according to the present embodiment includes a light emitting element 11 that is a Fabry-Perot semiconductor laser, and a plurality of bandpass filters 12a that pass only light having specific wavelengths different from laser light output from the light emitting element. , 12b, 12c,..., And an optical switch 13 that switches which band pass filter the laser beam output from the light emitting element is passed in accordance with a switching input from the outside. The light emitting element 11 is preliminarily configured to emit light at a wavelength that can pass through the plurality of bandpass filters 12a, 12b, 12c.

By providing the above configuration, the wavelength tunable optical transmission module 10 can obtain laser light of an arbitrary wavelength with sufficient accuracy without using a DFB laser or a Peltier element (TEC). Become.
Hereinafter, this will be described in more detail.

  FIG. 1 is an explanatory diagram showing a configuration of a wavelength tunable optical transmission module 10 according to the first embodiment of the present invention. The wavelength tunable optical transmission module 10 includes a light emitting element 11, bandpass filters 12a, 12b, 12c,... And an optical switch 13, each of which is connected by an optical waveguide. Although FIG. 1 shows an example including four bandpass filters 12a to 12d, the number of bandpass filters may be other than this.

  The light emitting element 11 is an FP laser (Fabry-Perot type semiconductor laser). FIG. 2 is an explanatory diagram showing an optical spectrum of laser light output from the light emitting element 11 shown in FIG. 2 and 6, the light emitting element 11 outputs laser light having a plurality of oscillation wavelengths λ1, λ2, λ3. Each of the bandpass filters 12a, 12b, 12c,... Has a characteristic that allows light having wavelengths substantially equal to the oscillation wavelengths λ1, λ2, λ3,.

  These wavelengths λ1, λ2, λ3,..., So that the wavelength tunable optical transmission module 10 should oscillate, that is, match the wavelength required as the frequency to be used. 12b, 12c ... are pre-designed. Since the specific design method belongs to the category of known technology, it is omitted here.

  The optical switch 13 switches the bandpass filters 12a, 12b,... Through which the laser light output from the light emitting element 11 is passed according to a switching input from the outside. The laser light that has passed through the bandpass filters 12a, 12b,... Is output to the outside of the wavelength tunable optical transmission module 10. The optical switch 13 is typically an MZ (Mach-Zehnder) interferometer type optical switch formed on a PLC, but may be based on other methods.

  FIG. 3 is an explanatory diagram showing the optical spectrum of the laser light that has passed through the bandpass filter 12a shown in FIG. FIG. 3A shows the case where the bandpass filter 12a is selected by the optical switch 13, and FIG. 3B shows the case where the bandpass filter 12b is selected.

  In the case shown in FIG. 3 (a), only the light of λ1, which is a wavelength that can pass through the bandpass filter 12a, among the oscillation wavelengths λ1, λ2, λ3... Shown in FIG. You can see that In the case shown in FIG. 3B, only light having a wavelength λ2 that can pass through the bandpass filter 12b is output to the outside. The same applies to the wavelengths λ3 (bandpass filter 12c) and the subsequent wavelengths.

  In other words, when the wavelength tunable optical transmission module 10 is desired to output the wavelength λ1 to the outside, the optical switch 13 may be switched to select the bandpass filter 12a. If the wavelength tunable optical transmitter module 10 is desired to output the wavelength λ2 to the outside, the optical switch 13 may be switched to select the bandpass filter 12b. The same applies to the wavelength λ3 and beyond.

  The band-pass filters 12a, 12b,... Have a smaller change in frequency characteristics due to heat than the light-emitting element 11. Therefore, even if the oscillation wavelength of the light-emitting element 11 may slightly change due to its own operating heat, the intensity of light passing through the band-pass filters 12a, 12b, 12c. The changes in the wavelengths λ1, λ2, λ3. That is, the wavelength tunable optical transmission module 10 does not cause any particular problem in practice even if a Peltier element (TEC) is not provided.

  Further, as described in Non-Patent Document 1 described above, the Fabry-Perot semiconductor laser emits light of a plurality of wavelengths at the same time. Therefore, if the communication speed is increased, signal superimposition occurs. It is said that it is not suitable. In the wavelength tunable optical transmission module 10 of the present embodiment, only the light that has passed through the bandpass filters 12a, 12b, 12c... Selected by the optical switch 13 is output. Even without this, the communication speed can be made faster than a single FP laser.

(Overall operation of the first embodiment)
Next, the overall operation of the above embodiment will be described.
The wavelength selection method according to the present embodiment operates a light emitting element that is a Fabry-Perot type semiconductor laser to oscillate and output laser light, and the oscillated output laser light passes only light of a specific wavelength provided in advance. An optical switch selects which of a plurality of different bandpass filters is passed according to an external switching input, and the selected bandpass filter selectively outputs light of a specific wavelength from the laser light.
By this operation, this embodiment has the following effects.

  According to the wavelength tunable optical transmission module 10 of the present embodiment, laser light having an arbitrary wavelength can be practically used in WDM communication without using a cooling element such as a DFB laser or a Peltier element (TEC). It can be obtained with accuracy. The wavelength-tunable optical transmission module 10 is inexpensive because it uses an FP laser instead of a DFB laser, and has low power consumption because it does not use a Peltier element (TEC). Further, it is not necessary to perform operations such as control and switching by the control device including the microprocessor as shown in FIG. This also causes cost reduction.

(Second Embodiment)
The wavelength tunable optical transmission module 110 according to the second embodiment of the present invention includes an SOA 114 (semiconductor optical amplifier) that amplifies and outputs the light that has passed through the bandpass filter in addition to the configuration of the first embodiment described above. ). In addition, the light emitting element 11, the optical switch 13, and the bandpass filters 12a, 12b, 12c... Are all mounted on the same PLC 110a (planar optical waveguide type optical circuit).

Even with the above configuration, the wavelength tunable optical transmission module 110 can obtain the same effects as those of the first embodiment, in addition to the bandpass filters 12a, 12b, 12c,. It is possible to make the laser light attenuated by passing through a light intensity that can withstand practical use. In addition, a simpler configuration can be provided at a low cost and in a small size.
Hereinafter, this will be described in more detail.

  FIG. 4 is an explanatory diagram showing the configuration of the wavelength tunable optical transmission module 110 according to the second embodiment of the present invention. The wavelength tunable optical transmission module 110 includes the same light emitting element 11, band-pass filters 12a, 12b, 12c,..., And an optical switch 13 as those in the first embodiment, and these are connected by an optical waveguide. The operations of the light-emitting element 11, the band-pass filters 12a, 12b, 12c,... And the optical switch 13 are the same as those in the first embodiment, and thus the description of the operation is omitted here.

  Then, the laser beams output from the bandpass filters 12a, 12b, 12c,... Are aggregated again by the optical waveguide and input to the SOA 114 (semiconductor optical amplifier). The SOA 114 amplifies the laser light and outputs it to the outside of the wavelength tunable optical transmission module 110. The light emitting element 11, the bandpass filters 12a, 12b, 12c,..., The optical switch 13, and the SOA 114 are all mounted on the PLC 110a (planar optical waveguide type optical circuit).

  When the laser light emitted by the light emitting element 11 passes through the bandpass filters 12a, 12b, 12c,. In the present embodiment, by inserting the SOA 114, the attenuation is compensated, and the light intensity can withstand practical use. In addition, since all the elements are mounted on the same PLC 110a, the manufacturing cost is reduced and the entire apparatus is downsized.

(Overall operation of the second embodiment)
Next, the overall operation of the above embodiment will be described.
The wavelength selection method according to the present embodiment operates a light emitting element that is a Fabry-Perot type semiconductor laser to oscillate and output laser light, and the oscillated output laser light passes only light of a specific wavelength provided in advance. The optical switch selects which of the different band-pass filters to pass according to the switching input from the outside, and the selected band-pass filter selectively outputs light of a specific wavelength from the laser light and is selected and output SOA (semiconductor optical amplifier) amplifies and outputs light of a specific wavelength.
By this operation, this embodiment has the following effects.

  The wavelength tunable optical transmission module 110 according to the present embodiment can also be attenuated by passing through the bandpass filters 12a, 12b, 12c,. It is possible to output a laser beam with a light intensity that can withstand practical use.

(Third embodiment)
The wavelength tunable optical transmission module 210 according to the third embodiment of the present invention is a MEMS (micro electro mechanical system) that is a member that performs an operation of switching the optical switch 213 in addition to the configuration of the first embodiment described above. ).

Even with the above configuration, the wavelength tunable optical transmission module 110 can obtain the same effects as those of the first embodiment.
Hereinafter, this will be described in more detail.

  FIG. 5 is an explanatory diagram showing the configuration of the wavelength tunable optical transmission module 110 according to the third embodiment of the present invention. The wavelength tunable optical transmission module 210 includes the same light-emitting element 11, band-pass filters 12a, 12b, 12c,... Then, the optical switch 13 configured by the MZ (Mach-Zehnder) interferometer type optical switch formed on the PLC is replaced with another optical switch 213 configured by MEMS (Micro Electro Mechanical Systems). Has been.

  Since the operations of the light-emitting element 11, the band-pass filters 12a, 12b, 12c,..., The optical switch 213, and the SOA 114 are the same as those in the first and second embodiments, the description of the operation is omitted here.

  Even with the above configuration, the same effects as those of the first and second embodiments can be obtained. The specific configuration of the optical switch may be realized by a mechanism other than MEMS or the MZ interferometer type optical switch (shown in the first or second embodiment).

  The present invention has been described with reference to the specific embodiments shown in the drawings. However, the present invention is not limited to the embodiments shown in the drawings, and any known hitherto provided that the effects of the present invention are achieved. Even if it is a structure, it is employable.

  Regarding the embodiment described above, the main points of the new technical contents are summarized as follows. In addition, although part or all of the said embodiment is summarized as follows as a novel technique, this invention is not necessarily limited to this.

(Appendix 1) A light-emitting element that is a Fabry-Perot semiconductor laser;
A plurality of bandpass filters that pass only light of specific wavelengths different from each other from the laser light output from the light emitting element;
A wavelength tunable optical transmission module, comprising: an optical switch that switches according to a switching input from the outside which of the bandpass filters the laser light output from the light emitting element is passed through.

(Supplementary note 2) The wavelength tunable optical transmission module according to supplementary note 1, wherein the light emitting element is configured in advance to emit light at a wavelength that can pass through the plurality of bandpass filters.

(Supplementary note 3) The wavelength tunable optical transmission module according to supplementary note 1, further comprising an SOA (semiconductor optical amplifier) that amplifies and outputs light that has passed through the bandpass filter.

(Supplementary note 4) The wavelength according to Supplementary note 1, wherein the light emitting element, the optical switch, and the band-pass filters are all mounted on the same PLC (planar optical waveguide type optical circuit). Variable optical transmitter module.

(Supplementary note 5) The wavelength tunable optical transmission module according to supplementary note 1, characterized by not including a cooling element that cools the light emitting element, the optical switch, and the band-pass filters.

(Supplementary note 6) The wavelength tunable optical transmission module according to supplementary note 1, wherein the optical switch is a Mach-Zehnder interferometer type optical switch.

(Supplementary note 7) The wavelength tunable optical transmission module according to supplementary note 1, wherein the optical switch is equipped with a MEMS (micro electro mechanical system) that is a member that executes a switching operation.

(Appendix 8) A light emitting element that is a Fabry-Perot type semiconductor laser is operated to oscillate and output a laser beam,
The optical switch selects, depending on the switching input from the outside, whether to pass the oscillation output laser light through a plurality of different bandpass filters that pass only light of a specific wavelength provided in advance,
The wavelength selection method, wherein the selected bandpass filter selectively outputs light of the specific wavelength from the laser light.

(Supplementary note 9) The wavelength selection method according to supplementary note 8, wherein an SOA (semiconductor optical amplifier) amplifies and outputs the light having the specific wavelength selected and output.

(Supplementary note 10) The wavelength selection method according to supplementary note 8, wherein the light emitting element is configured in advance to emit light at a wavelength that can pass through the plurality of bandpass filters.

(Additional remark 11) The said light emitting element, the said optical switch, and each said band pass filter are all mounted on the same PLC (planar optical waveguide type optical circuit), Additional remark 8 characterized by the above-mentioned. Wavelength selection method.

(Supplementary note 12) The wavelength selection method according to supplementary note 8, wherein the wavelength selection method is configured in advance so as not to include a cooling element that cools the light emitting element, the optical switch, and the band-pass filters. .

(Supplementary note 13) The wavelength selection method according to supplementary note 8, wherein the optical switch is configured in advance by a Mach-Zehnder interferometer type optical switch.

(Supplementary note 14) The wavelength selection method according to supplementary note 8, wherein the optical switch is equipped with a MEMS (micro electro mechanical system) that is a member that executes a switching operation.

  The present invention can be applied to a wavelength tunable optical transmission module used in an optical transmission network. In particular, it is suitable for use in CWDM (Coarse Wavelength Division Multiplexing) with a relatively wide wavelength interval, but can also be used for DWDM (Dense Wavelength Division Multiplexing) with a narrow wavelength interval.

10, 110, 210 Wavelength variable type optical transmission module 11 Light emitting element 12a, 12b, 12c, 12d Band pass filter 13, 213 Optical switch 110a PLC
114 SOA

Claims (7)

A light emitting device which is a Fabry-Perot type semiconductor laser;
A plurality of bandpass filters that pass only light of specific wavelengths different from each other from the laser light output from the light emitting element;
A wavelength tunable optical transmission module, comprising: an optical switch that switches according to a switching input from the outside which of the bandpass filters the laser light output from the light emitting element is passed through.   The wavelength tunable optical transmission module according to claim 1, wherein the light emitting element is configured in advance to emit light at a wavelength that can pass through the plurality of bandpass filters.   2. The wavelength tunable optical transmission module according to claim 1, further comprising an SOA (semiconductor optical amplifier) that amplifies and outputs light that has passed through the bandpass filter.   2. The wavelength tunable light according to claim 1, wherein the light emitting element, the optical switch, and the band-pass filters are all mounted on the same PLC (planar optical waveguide optical circuit). Transmission module.   The wavelength tunable optical transmission module according to claim 1, further comprising a MEMS (micro electro mechanical system) that is a member that performs a switching operation as the optical switch. Operate a light emitting element that is a Fabry-Perot type semiconductor laser to oscillate and output laser light,
The optical switch selects, depending on the switching input from the outside, whether to pass the oscillation output laser light through a plurality of different bandpass filters that pass only light of a specific wavelength provided in advance,
The wavelength selection method, wherein the selected bandpass filter selectively outputs light of the specific wavelength from the laser light.   The wavelength selection method according to claim 6, wherein an SOA (semiconductor optical amplifier) amplifies and outputs the light of the specific wavelength selected and output.

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