JP4230934B2 - Multi-channel optical modulator and multi-channel optical transmitter - Google Patents

Description

  The present invention relates to a multi-channel optical modulation device and a multi-channel optical transmission device used in optical information communication and the like.

  In recent years, optical communication has been used in many information communication networks due to its large capacity and ultra-high speed. In such an optical communication network, optical semiconductor components such as a light emitting element and a light receiving element are widely used, and their research and development are active. Research and development of optical semiconductor components include not only individual components such as semiconductor lasers (LD), photodiodes (PD), and optical modulators (EAM), but also active optical devices such as LDs and multimode interferometers (MMI). ) And passive optical devices typified by arrayed waveguide gratings (AWG) are also monolithically integrated on a semiconductor substrate.

  In order to realize a large capacity of optical communication, a wavelength division multiplexing (WDM) transmission system that propagates a large number of optical signals having different wavelengths in a fiber is used. In this method, since a large number of optical signals can be transmitted through a single fiber, a large capacity can be realized at low cost. In this case, it is necessary to prepare a large amount of light of different wavelengths, that is, a large number of channels, and the cost reduction is very important.

  In order to realize such a light source, it is desirable that a single semiconductor laser can generate multi-wavelength light. For example, a multi-wavelength generation light source using a supercontinuum light source or a mode-locked semiconductor laser has been developed. . In such a light source, a plurality of channel lights corresponding to each channel are output in a lump, so a multi-channel light modulation device capable of separating each channel light and modulating it into individual optical signals is required.

Y. Suzaki et al., “2.5-Gb / s Operation of Monolithically Integrated Eight-Channel WDM Modulator Module with 25-GHz Channel Spacing” Technical Digest of Optical Fiber Communication conference & exposition, TuG4, 2003 IEICE technical report VOL. 103, NO. 272 (OPE 2003 118-130) PAGE. 35-38, 2003 "Monolithic integrated multi-channel modulator"

  As shown in FIG. 5, such a multi-channel optical modulation device 10 includes a demultiplexer 11, an optical modulator 12, and a multiplexer 13 (for example, Y. Suzaki et al., “2.5 -Gb / s Operation of Monolithically Integrated Eight-Channel WDM Modulator Module with 25-GHz Channel Spacing ”Technical Digest of Optical Fiber Communication conference & exposition, TuG4, 2003).

  Incident light is demultiplexed into each channel by a demultiplexer 11 and coupled to an optical waveguide having the number of channels. After that, the optical modulator 12 receives the modulation, and the multiplexer 13 multiplexes all the channel lights to the output port and outputs them.

  In general, the multi-wavelength generation light source 1 outputs a larger number of channel lights than the number of channels of the multi-channel light modulator 10, so that a multiplexer / demultiplexer (demultiplexer 11 and multiplexer 13) is necessary. Only the right channels need to be extracted. On the other hand, the multiplexer / demultiplexer (the demultiplexer 11 and the multiplexer 13), in principle, multiplexes and demultiplexes light of different wavelengths having different diffraction orders at the same port. The interval between wavelengths that differ by one order is called FSR (Free Spectral Range).

  Therefore, in order to multiplex / demultiplex only light having a desired wavelength from a desired port, the number of channels of light output from the multi-wavelength light source is used as the FSR of the multiplexer / demultiplexer (demultiplexer 11 and multiplexer 13). Is designed so that other channel light does not enter the same port.

Consider the construction of the following transmission system. The number of channels (wavelengths) used at the same time is 8, and 8 blocks can be switched to 16 blocks, and a total of 128 channels are handled. As an application example, there are 16 transmission destination nodes, and eight channels are assigned to each of them, and the transmission destination node can be selected by switching blocks.

  If a conventional multi-channel light modulation device is used in this system, only a specific 8ch can be handled. Therefore, as shown in FIG. 3A, 16 multi-channel light modulation devices 10-1 to 10- of different designs are used. It is necessary to change the optical path by the optical switch 3 or the like every time the blocks of the multi-wavelength generating light source 1 with variable wavelength are switched in parallel. In this case, the apparatus shown in FIG. 5 is individually prepared for each block, and the yield is greatly reduced in consideration of manufacturing errors and the like as compared with the case where the same apparatus is substituted.

The configuration of the multi-channel optical modulator according to the present invention for solving the above problems is as follows.
From a multi-wavelength light source that can change the wavelength in units of blocks by making N channel light of different wavelengths and guard channel light of 0 channel or several channels into one block and moving the center wavelength of the generated channel light by FSR A multi-channel light modulation device to which light is input,
A demultiplexer for demultiplexing and outputting to N channels when light generated from the multi-wavelength generation light source is incident;
A plurality of optical modulators that individually input the light of each channel demultiplexed by the demultiplexer, modulate and output the input light, and
A multiplexer for multiplexing and outputting the light of each channel modulated by the optical modulator,
In addition, the duplexer has an FSR having a wavelength width corresponding to the one block.

The configuration of the multi-channel optical modulator according to the present invention is as follows:
It is monolithically integrated on the same semiconductor substrate.

The configuration of the multi-channel optical transmitter according to the present invention is as follows.
A multi-wavelength generating light source capable of changing the wavelength in units of blocks by moving N channel lights of different wavelengths and guard channel light of 0 channel or several channels into one block and moving the center wavelength of the generated channel light by FSR ,
A multi-channel optical modulator,
The multi-channel light modulator is
A demultiplexer for demultiplexing and outputting to N channels when light generated from the multi-wavelength generation light source is incident;
A plurality of optical modulators that individually input the light of each channel demultiplexed by the demultiplexer, modulate and output the input light, and
A multiplexer for multiplexing and outputting the light of each channel modulated by the optical modulator,
In addition, the duplexer has an FSR having a wavelength width corresponding to the one block.

The configuration of the multi-channel optical transmitter according to the present invention is as follows.
The multi-channel light modulation device is monolithically integrated on the same semiconductor substrate.

The configuration of the multi-channel optical transmitter according to the present invention is as follows.
The multi-wavelength generating light source and the multi-channel light modulator are monolithically integrated on the same semiconductor substrate.

  According to the present invention, it is possible to realize a multi-channel optical modulation device that can cope with channel light of different wavelengths with one or a small number of differently designed elements, and can greatly improve productivity and cost. Device and multi-channel optical transmitter can be realized.

  The best mode for carrying out the present invention will be described in detail below.

  FIG. 1A shows a basic configuration of the present invention. This multi-channel optical transmission apparatus includes a multi-wavelength generation light source 101 and a multi-channel light modulation apparatus 110.

  The multi-wavelength generation light source 101 generates and outputs light having a channel number N or more and a block channel number or less. Various forms of the multi-wavelength generation light source 101 are conceivable, and generation from several waves to several hundred waves is possible. However, since it is necessary to reduce the pulse width in order to increase the number of generated lines, it is difficult to generate stably. In addition, since the light intensity is distributed to each wavelength light, the light intensity of each wavelength becomes weak as a result, which may cause a problem in practice. Therefore, as a simple multi-wavelength light source 101, a light source capable of stably generating a dozen waves with high light intensity is desirable in practice. This multi-wavelength generation light source 101 is a light source that can change the wavelength in units of blocks, with N channel lights having different wavelengths and 0-channel or several-channel guard channel light as one block.

  The multi-channel optical modulator 110 includes N optical modulators 112 and a multiplexer / demultiplexer (demultiplexer 111 and multiplexer 113) having FSRs corresponding to the blocks, and the multi-wavelength light source 101 described above. Even if the block wavelength is changed, the number of channels can be covered only by preparing the same element or a small number of elements having different designs by designing the optical modulator 112 to modulate the block wavelength.

That is, the duplexer 111 has an FSR having a wavelength width corresponding to the one block, and the multiplexer 113 also has an FSR having a wavelength width corresponding to the one block.
Note that it is not necessary for any of the multiplexers / demultiplexers (the demultiplexer 111 and the multiplexer 113) to have an FSR having a wavelength width corresponding to the one block. It is only necessary to have an FSR having a wavelength width corresponding to the block.

  The basic principle is as follows. First, when a plurality of channel lights are incident on the multi-channel light modulator 110, the incident channel light is demultiplexed by the demultiplexer 111. Here, the N channel lights are coupled to the respective optical waveguides, but the other lights in the FSR, that is, the light of the guard channel cannot be coupled to the waveguides, and thus are all removed. The N channel lights pass through the modulator 112 and the multiplexer 113 and are output from the output port. In this way, it is possible to selectively modulate only the necessary channel light by setting the wavelength width of the channel light generated by the multi-wavelength light source 101 to be FSR or less.

  Here, if the center wavelength of the channel light generated by the multi-wavelength generation light source 101 is moved by the FSR as shown in FIG. 1B, the multi-channel light modulation device 110 requires N channels as described above. Only light is selected, modulated, and output from the output port. Thus, even if the same apparatus is used, it becomes possible to modulate channel light having different wavelengths.

  For example, by setting the FSR of the multiplexer / demultiplexer (the demultiplexer 111 and the multiplexer 113) to N which is the same as the number of channels, all the channels can be covered with one type of element. When N is 8, the number of channel lights output from the light source is 8, and the number of channels required for the entire system is 128, the conventional example requires 16 types of elements having different designs as described above. On the other hand, the present invention can cope with one type of element.

  This is because it is sufficient to produce a large amount of all the elements with the same design, so that productivity can be greatly improved in terms of yield. However, in general, the number of channel lights generated from a multi-wavelength light source such as a mode-locked LD cannot be strictly controlled. Therefore, when such a guard channel is not used, unnecessary channel light is removed. It is thought that the wavelength filter of this is needed.

  When the number of channels output from the multi-wavelength generation light source 101 is 16, which is twice N, the FSR of the multiplexer / demultiplexer (demultiplexer 111 and multiplexer 113) is twice N. By setting the number to 16, a necessary channel can be modulated, and unnecessary channel light can be removed because it is not coupled to the waveguide. In this case, it is necessary to prepare two types of elements having different designs, but the productivity can still be greatly improved as compared with the conventional 16 types.

  Further, if all the elements are integrated on the InP substrate, the optical axis adjustment points between the elements can be greatly reduced as compared with the case where the elements are manufactured as individual elements. For example, in the above case, there are a total of 16 connection portions between the multiplexer / demultiplexer (the demultiplexer 111 and the multiplexer 113) and the optical modulator 112, but in the monolithic integration, these optical axis adjustments are not necessary. Therefore, it is possible to simplify and reduce the mounting process.

  As described above, in the multi-channel light modulation device of the present invention, it is possible to deal with a large number of channels by preparing a small number of elements, and the productivity can be greatly improved.

  A multi-channel optical transmission apparatus according to an embodiment of the present invention will be described below with reference to FIG. The multi-channel optical transmission apparatus according to this embodiment includes a multi-wavelength generation light source 201 and a multi-channel optical modulation apparatus 210.

  The multi-channel optical modulator 210 is configured by integrating two AWGs 211 and 212 serving as multiplexers / demultiplexers, an EAM array 213 corresponding to the number of channels, and a connection waveguide 214 on an InP substrate. Here, the number of channels is 8, and the FSRs of both AWGs 211 and 212 have a wavelength width of 16 channels that is twice the number of channels. In addition, lenses 220 and 221 for inputting and outputting optical signals are provided.

In actual device fabrication, first, on the n-InP substrate, a GaInAsP EAM active layer and a p-InP clad layer are formed in the EAM region, and a GaInAsP AWG waveguide layer and an i-InP clad layer are formed in the AWG region and the connection waveguide region. Are selectively grown by metal organic vapor phase epitaxy. Next, all waveguide layers are processed into a high mesa structure by Cl ₂ reactive ion etching. In addition, an electrode is formed in the EAM array in order to apply a reverse voltage. The input / output waveguides on both end faces are provided with anti-reflection coating.

  The multi-wavelength generation light source 201 uses a mode-locked light source including an active region 202, a modulation region 203, and a DBR region 204. The modulation region 202 performs a mode lock operation by supplying a modulation signal having a frequency corresponding to the channel interval, and generates about 10 channel lights by setting the DBR reflection band to a wavelength width of 8 channels. . The generated light is emitted through the lens 205.

  The light output from the multi-wavelength light source 201 is connected to the multi-channel light modulator 210 via the lens 220 through the optical fiber 222, and an individual modulation signal is supplied to each EAM array 213 of the multi-channel light modulator 210. By applying, optical signals of only 8 channels can be output. The optical signal output from the multi-channel light modulator 210 is sent out through the lens 221 and the optical fiber 223.

Here, the difference between the conventional example and the present invention is simply shown by a specific system configuration.
As described above, consider the construction of the following transmission system. The number of channels (wavelengths) used at the same time is 8, and 8 blocks can be switched to 16 blocks, and a total of 128 channels are handled.

  At this time, a multi-wavelength generating light source having about 10 channels of output light is used, and the wavelength wavelength function is used so that the channel wavelength can be switched corresponding to 16 blocks. In the multi-channel optical modulator, the FSR of the multiplexer / demultiplexer is added with a guard channel to 16 channels so that unnecessary light other than the 8 waves used simultaneously can be removed.

  When a conventional multi-channel light modulator is used in this system, only one block can be handled as described above. Therefore, as shown in FIG. 3A, 16 multi-channel light modulators 10- having different designs are used. 1 to 10-16 are arranged in parallel, and the optical path must be changed by the optical switch 3 or the like every time the block of the multi-wavelength generating light source 1 is switched.

  On the other hand, in the present invention, as shown in FIG. 3B, the same function can be realized by connecting only one multi-channel light modulator 110 to the multi-wavelength generating light source 101, and the size and cost can be greatly reduced. (The required volume and cost of the light modulation device are reduced to 1/16).

  The above is the case where the present invention is most effective in the case where the number of channels used at the same time is the same as the number of channels of the multi-channel optical modulation device, but it is still effective even when the number of channels used simultaneously increases. Consider a case where the number of channels used simultaneously increases to 128.

  In the conventional multi-channel light modulation device, as shown in FIG. 4A, it is necessary to arrange 16 types of multi-channel light modulation devices 10-1 to 10-16 having different designs in parallel. Reference numeral 4 denotes a 16 × 1 optical coupler.

  In the present invention, as shown in FIG. 4 (b), it is necessary to arrange 16 multi-channel light modulators 110 in parallel. However, the major difference is that only two different designs are required. . Thereby, as described above, the production yield of the elements can be greatly improved. Reference numeral 120 denotes a 16 × 1 optical coupler.

  The present invention can be applied to a multi-channel optical transmission apparatus that can support multi-channels by preparing a small number of types of elements even if the block of the multi-wavelength generating light source is switched.

The block diagram which shows the basic composition of the multichannel optical transmission apparatus of this invention. The block diagram which shows the basic composition of the multichannel optical transmission apparatus of this invention. 1 is a configuration diagram showing a multi-channel optical transmitter according to an embodiment of the present invention. The block diagram which shows the multichannel optical transmission apparatus using the conventional multichannel optical modulation apparatus. The block diagram which shows the multichannel optical transmission apparatus using the multichannel optical modulation apparatus of this invention. The block diagram which shows the multichannel optical transmission apparatus using the conventional multichannel optical modulation apparatus. The block diagram which shows the multichannel optical transmission apparatus using the multichannel optical modulation apparatus of this invention. The block diagram which shows the conventional multichannel optical transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multiwavelength light source 3 Optical switch 4 Optical coupler 10, 10-1 to 10-16 Multichannel light modulator 11 Demultiplexer 12 Optical modulator 13 Multiplexer 101 Multiwavelength light source 110 Multichannel light modulator 111 Demultiplexer 112 Optical modulator 113 Multiplexer 201 Multi-wavelength generating light source 202 Active region 203 Modulating region 204 DBR region 205 Lens 210 Multichannel light modulator 211, 212 AWG
213 EAM array 214 Connecting waveguide 220, 221 Lens 223, 224 Optical fiber

Claims (5)

From a multi-wavelength light source that can change the wavelength in units of blocks by making N channel light of different wavelengths and guard channel light of 0 channel or several channels into one block and moving the center wavelength of the generated channel light by FSR A multi-channel light modulation device to which light is input,
A demultiplexer for demultiplexing and outputting to N channels when light generated from the multi-wavelength generation light source is incident;
A plurality of optical modulators that individually input the light of each channel demultiplexed by the demultiplexer, modulate and output the input light, and
A multiplexer for multiplexing and outputting the light of each channel modulated by the optical modulator,
Moreover, the duplexer has an FSR having a wavelength width corresponding to the one block. Oite to claim 1,
The multi-channel light modulation device is monolithically integrated on the same semiconductor substrate. A multi-wavelength generating light source capable of changing the wavelength in units of blocks by moving N channel lights of different wavelengths and guard channel light of 0 channel or several channels into one block and moving the center wavelength of the generated channel light by FSR ,
A multi-channel optical modulator,
The multi-channel light modulator is
A demultiplexer for demultiplexing and outputting to N channels when light generated from the multi-wavelength generation light source is incident;
A plurality of optical modulators that individually input the light of each channel demultiplexed by the demultiplexer, modulate and output the input light, and
A multiplexer for multiplexing and outputting the light of each channel modulated by the optical modulator,
In addition, the duplexer has an FSR having a wavelength width corresponding to the one block. Oite to claim 3,
The multi-channel optical modulator is monolithically integrated on the same semiconductor substrate. Oite to claim 3 or claim 4,
A multi-channel optical transmitter characterized in that the multi-wavelength generating light source and the multi-channel optical modulator are monolithically integrated on the same semiconductor substrate.

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