JP5579817B2 - Optical-optical serial-parallel converter for multi-wavelength optical signals - Google Patents

Description

  The present invention relates to an optical-optical serial-parallel conversion device that performs serial-parallel conversion of all light of a multi-wavelength optical signal used in optical information communication or the like.

  Optical communication has the features of large capacity and ultra-high speed, and has been put into practical use in many information communication networks in recent years. At high speeds of about 10 Gbps, even if an optical signal is transmitted over several tens of kilometers over an optical fiber, the waveform degradation of the optical signal due to optical fiber loss or dispersion is minimal, so all information is superimposed on one wavelength. Is generally transferred.

  However, at high speeds exceeding 40 Gbps and 100 Gbps, the waveform deterioration of the optical signal due to the dispersion of the optical fiber cannot be ignored. Furthermore, such high-speed signals cannot be processed by CMOS electronic circuits using silicon, which is currently the most common and can be produced at low cost. Therefore, for example, 20 Gbps × 2 wavelengths at 40 Gbps and 25 G × 4 wavelengths at 100 Gbps are used to transmit and receive information by superimposing divided information on optical signals having a plurality of wavelengths.

  Even in this case, the electronic circuit needs to directly process an electrical signal exceeding 20 Gbps. For this purpose, a silicon-based CMOS requires a step of further reducing the line width, or the material system is made of silicon germanium or indium. It is necessary to use a compound semiconductor such as phosphorus or a bipolar transistor. Use of the compound semiconductor as described above causes an increase in power consumption and an increase in manufacturing cost.

  Therefore, these problems can be solved if a serial-parallel converter capable of reducing the speed at the optical signal stage can be realized. As a conventional optical-optical type serial-parallel conversion device having the above-mentioned function, there is one as disclosed in Patent Document 1. A conventional optical-optical serial-parallel conversion device is shown in FIGS. 5A and 5B, and its basic operation will be described below. In FIGS. 5A and 5B and FIG. 6 described later, the dotted waveform indicates the signal “0” and the solid waveform indicates the signal “1”. In the following description, M and N are natural numbers of 2 or more.

In the conventional optical-optical serial-parallel converter 50, an optical packet (serial light Ls) is input to a 1: N optical splitter 51, and the input serial light Ls is branched to a parallel number N. Each of the parallel optical signals Ld _{1 to} Ld _N is given a delay that is sequentially shifted by a time of 1 bit by using each optical delay line 52a. Thereafter, the sequentially delayed parallel optical signals Ld _{1 to} Ld _N are input to the polarization beam splitter (PBS) 54 via the input side fiber array 52 and the microlens array 53 a, reflected, and then passed through the condenser lens 55. Thus, the light is condensed at one point of the surface optical switch 56. In this way, in the sequentially delayed parallel optical signals Ld _{1 to} Ld _N , the time window Tw in which all the bits from the first bit to the Nth bit are condensed on one point of the surface optical switch 56 at the same time. (See FIG. 5B).

  In this time window Tw, when a control light pulse Pc prepared in advance is incident on the surface optical switch 56 via the mirror 57 and the reflectance of the surface optical switch 56 is changed, the same time is taken. Only the bit light collected at one point is reflected and output to the output port of the PBS 54, and is output via the microlens array 53 b and the output side fiber array 58. As a result, 1-to-N optical-optical serial-parallel conversion is realized. After the converted parallel light Lp is photoelectrically converted by N PDs 59, the bit rate of the serial light Ls is 1 / N. It can be processed by a low-speed electronic circuit having a bandwidth.

Japanese Patent No. 3577289

However, when the optical packet of M wavelengths is converted by the optical-optical serial-parallel converter 50 as described above, if it is input as it is, light of multiple wavelengths is simultaneously incident on the PD 59 at the same time. Therefore, interference occurs between the parallel lights Lp having a plurality of wavelengths. Therefore, as shown in FIG. 6, demultiplexes into M serial optical Ls ₁ ~Ls _M for each wavelength in advance multiwavelength serial optical Lm by the wavelength demultiplexer 61, the M light - optical type serial - enter the serial light Ls ₁ ~Ls _M of wavelengths lambda ₁ to [lambda] _M to parallel converter 50 ₁ to 50 _M, the serial - it is necessary to handle the parallel conversion. If it does in this way, the apparatus for control light pulses Pc and PD for reception will also increase with the increase in the serial-parallel converters 50 ₁ to 50 _M , and the cost will increase due to these increases. Furthermore, since multi-wavelength optical packets are processed synchronously in the electronic circuit, it is necessary to adjust the delay in each of the serial-parallel converters 50 ₁ to 50 _M as a whole, resulting in an increase in cost.

  The present invention has been made in view of the above problems, and provides an optical-optical serial-parallel conversion device for multi-wavelength optical signals which can be reduced in cost and size and can easily adjust the reception timing between the multi-wavelength optical signals. The purpose is to provide.

An optical-optical serial-parallel conversion device for a multi-wavelength optical signal according to the first invention for solving the above-mentioned problems
Light of a multi-wavelength optical signal, which is composed of optical signals of M wavelengths having the same transmission speed and serial-parallel converts 1: N into a multi-wavelength optical signal in which the first bits of the M optical signals are aligned at the same time. An optical serial-parallel converter,
A serial-parallel converter that outputs each bit to N output ports at different positions for every N bits of the multi-wavelength optical signal, and performs serial-parallel conversion to 1: N;
A delay unit connected to each of the output ports, separating optical signals having M wavelengths output from the output ports for each wavelength, converting the optical signals into electrical signals, and sequentially delaying the electrical signals at equal intervals It has a door,
The serial-parallel converter is
A demultiplexer for demultiplexing the multi-wavelength optical signal into N parallel optical signals;
An optical delay unit that sequentially delays each of the N parallel optical signals demultiplexed by the demultiplexer by 1 bit;
A polarized beam that reflects the N parallel optical signals delayed by the optical delay unit, transmits an optical signal having a polarization direction different from that of the N parallel optical signals, and outputs the optical signal to the N output ports. A splitter,
A lens that condenses the N parallel optical signals reflected by the polarization beam splitter at one point;
An optical switch that is arranged at one point condensed by the lens and changes the polarization direction of the N parallel optical signals collected and reflects to the polarization beam splitter while a predetermined optical pulse is being input. When,
An optical pulse that outputs the predetermined optical pulse at a timing at which the first to Nth bits of the N parallel optical signals sequentially delayed one bit at a time by the optical delay unit are condensed on the optical switch. A generator,
The delay unit is
An optical waveguide connected to the output port and formed on a planar optical circuit substrate or a compound semiconductor substrate;
M grating couplers formed in the optical waveguide and separating optical signals of different wavelengths,
M photodiodes each converting the optical signal separated by the grating coupler into the electrical signal;
M electrical delay lines for sequentially delaying the electrical light signals converted by the photodiodes at equal intervals for each electrical signal;
A main electrical delay line connected to the M electrical delay lines and for combining the delayed electrical signals .
However, M and N are natural numbers of 2 or more.

  According to the present invention, since a multi-wavelength optical signal can be serial-parallel converted as an optical signal using one serial-parallel converter and N delay units, the cost can be reduced and the size can be reduced. It is possible to realize an optical-optical serial-parallel conversion device for multi-wavelength optical signals that makes it easy to adjust the reception timing between optical signals.

(A) is a schematic block diagram which shows the reference example ( reference example 1) of embodiment of the optical-optical serial-parallel conversion apparatus of the multiwavelength optical signal which concerns on this invention, (b) is the delay part. It is a schematic block diagram which shows. It is a conceptual diagram explaining the serial-parallel conversion process in the optical-optical serial-parallel conversion apparatus of the multiwavelength optical signal shown in FIG. It is a schematic block diagram which shows the modification ( reference example 2) of the delay part shown in FIG.1 (b). It is a schematic block diagram which shows the other modification (Example 1 ) of the delay part shown in FIG.1 (b). (A) is a schematic block diagram which shows the conventional optical-optical type serial-parallel converter, (b) is a figure explaining the operation | movement with the surface type optical switch. It is a schematic block diagram which shows the structure in the case of processing a multi-wavelength optical signal using the conventional optical-optical type serial-parallel converter shown in FIG.

  Hereinafter, an embodiment of an optical-optical serial-parallel conversion apparatus for multi-wavelength optical signals according to the present invention will be described with reference to FIGS.

( Reference Example 1)
FIG. 1A is a schematic configuration diagram showing an optical-optical serial-parallel conversion device for a multi-wavelength optical signal of this reference example, and FIG. 1B is a schematic configuration diagram showing its delay unit. FIG. 2 is a conceptual diagram illustrating the serial-parallel conversion process. In FIGS. 1A and 1B, the dotted waveform indicates the signal “0”, and the solid waveform indicates the signal “1”. In the following description, M and N are natural numbers of 2 or more.

Light Serial - - light of multi-wavelength optical signal of the reference example parallel conversion device, as shown in FIG. 1, the serial - has parallel converter 10 and the N delay unit 20 ₁ to 20 _N.

In the serial-parallel conversion unit 10, for each N bits of the multi-wavelength serial light Lm, each bit is separated into _N output ports P _{1 to} P _N at different positions, and each output port P _{1 to} P _N to M The optical signals of a plurality of wavelengths are output, and the multi-wavelength serial light Lm is serial-parallel converted to 1: N.

  The serial-parallel converter 10 includes a 1: N optical splitter 11 (demultiplexer), an input-side fiber array 12 having an optical delay line 12a (delay unit), microlens arrays 13a and 13b, and a polarized beam. A splitter (PBS) 14, a condensing aspheric lens 15, a surface optical switch 16, a collimating fiber 17, 90-degree reflecting mirrors 18 a and 18 b, and an output side fiber array 19 are provided.

Then, serial - output side of the parallel converter 10, i.e., M in each of the output ports P ₁ to P _N of PBS 14, which via an output-side fiber array 19, output from the output port P ₁ to P _N the optical signal consisting of number of wavelengths, the delay unit 20 ₁ to 20 _N for giving sequential equally spaced delay for each wavelength are respectively connected.

The delay unit 20 ₁ to 20 _N is of the fiber type, the delay unit 20 ₁ one of them via the circulator 21 to be described later, the optical fiber of the output side fiber array 19 (output port P ₁₎ a connected optical fiber 22, are formed apart at equal intervals from each other in the optical fiber 22 to provide equally spaced delays, and M of the fiber grating 23 ₁ ~ 23 _M for reflecting the light signals of mutually different wavelengths, the output The optical signals inserted between the optical fibers (output port P ₁ ) of the side fiber array 19 and the optical fibers 22 and reflected by the _M fiber gratings 23 ₁ to 23 _M are separated from the optical fibers 22 and output. And an optical circulator 21. The optical fiber 22 is connected to one output port 21 a of the circulator 21, and the PD 24 is connected to the other output port 21 b of the circulator 21.

  Next, the basic operation of the serial-parallel conversion process in the present invention will be described with reference to the conceptual diagram shown in FIG. 2 together with FIG. In FIG. 2, as an example, M = 4 and N = 16 are described.

  First, on the transmission side, an optical packet (multi-wavelength serial light Lm) having the same characteristics (the same transmission speed and the same polarization direction), consisting of optical signals of M wavelengths and having different information for each wavelength is generated. (See FIG. 2 (a)). The generation may be performed by, for example, intensity-modulating CW light output from M DFB lasers using M LN modulators or EA modulators and multiplexing the light with an optical multiplexer. Here, if the overall transmission rate is T [bit / s], the transmission rate of the optical signal of each wavelength is T / M [bit / s], and the LN modulator and the EA modulator use this transmission rate. Driven. At this time, the modulation signal is driven so that the first bits of the optical signals of the respective wavelengths are aligned at the same time. The optical signal of each wavelength is linearly polarized and adjusted by a polarization controller or the like so that the polarization planes coincide.

  Such multi-wavelength serial light Lm is input to the serial-parallel converter 10. Here, as an example, a reflective surface optical switch 16 made of a semiconductor and using a differential spin polarization method is used. The configuration used is described. Even when other principles and methods are used, if the same time bits of the multi-wavelength serial light Lm are serial-parallel converted to different physical output positions, other principles and methods such as transmission type The present invention can also be applied to a configuration using a surface optical switch.

  When the multi-wavelength serial light Lm is input to the serial-parallel converter 10, first, the 1: N optical splitter 11 branches (splits) it into N parallel optical signals. The input-side fiber array 12 is composed of N optical fibers, and each includes an optical delay line 12a (delay unit). In each optical delay line 12a, each of the N parallel optical signals demultiplexed by the optical splitter 11 is sequentially delayed by one bit. The delayed N parallel optical signals become parallel light via the microlens array 13 a, reflected by the PBS 14, and condensed at one point of the surface optical switch 16 via the condensing aspherical lens 15. The The surface optical switch 16 is arranged at one point condensed by a lens.

The PBS 14 is composed of two right-angle prisms made of a transparent medium transparent to the multi-wavelength serial light Lm, and a dielectric polarizing film is formed on the slope of the right-angle prism. The dielectric polarizing film is set to reflect an optical signal having a predetermined polarization direction and transmit an optical signal having a polarization direction different from the polarization direction. Specifically, since the input N parallel optical signals are linearly polarized light, the N parallel optical signals reflected by the PBS 14 and reflected by the surface optical switch 16 are elliptically polarized as described later. Therefore, it is set so as to pass through the PBS 14 and output to the output ports P _{1 to} P _N.

Here, since each of the N parallel optical signals is sequentially delayed by one bit, in the sequentially delayed parallel optical signals (Ld _{1 to} Ld _N ), as shown in FIG. When all the bits from the first to the Nth bit are arranged in parallel at a certain same timing (time window Tw) and they enter the surface type optical switch 16, N bits are collected at one point at the same time. Will be.

At the timing of turning on and off the time window Tw, the circularly polarized control light pulse Pc ₁ of one spin and the circularly polarized control light pulse Pc ₂ of the other spin generated by an optical pulse generator (not shown) are generated. Then, the light enters the surface optical switch 16 through the collimating fiber 17 and the 90-degree reflecting mirrors 18a and 18b. Then, due to the effect of the differential spin polarization method, the reflected light from the planar optical switch 16 changes to elliptically polarized light only during the on and off time windows Tw and is reflected toward the PBS 14. That is, only the N bits collected at one point of the surface optical switch 16 during the time window Tw are reflected to the PBS 14. As a result, the reflected N bits pass through the PBS 14 and are serial-parallel converted and output to N physically separated output ports P _{1 to} P _N. At the output ports P _{1 to} P _N , the light is condensed by the microlens array 13 b and input to the output side fiber array 19.

Since the processes up to this point are common to each wavelength, each of the output ports P _{1 to} P _N (each optical fiber of the output-side fiber array 19) has M wavelengths of light that are serial-parallel converted. The signal is included.

The process from here is common to each of the output ports P _{1 to} P _N (each optical fiber of the output-side fiber array 19), and therefore will be described by focusing on _one output port P ₁ .

The output port P ₁ includes optical signals of M wavelengths that have been serial-parallel converted to 1 / N (see FIG. 2B). If this is the case, since M optical bits are at the same time, it is necessary to receive them separately in time. When attention is paid to an optical signal of a certain wavelength, there are optical bits at an N bit period. Therefore, if bits of M wavelengths can be arranged at regular intervals in the meantime, optical bits of each wavelength can be received by the same PD. This is realized by shifting the reflection position of the optical bit of each wavelength and inserting an appropriate delay therebetween. Therefore, as shown in FIG. 1 (b), equally spaced, each different wavelengths lambda ₁ to [lambda] _M M-number of the fiber grating 23 ₁ ~ 23 _M for reflecting light to the optical fiber 22.

  Next, with c being the speed of light and n being the equivalent refractive index of the optical fiber 22, the distance ΔL / 2 between the effective reflection points of each wavelength is obtained from the following equation.

  ΔL / 2 = (c / n) × ((N / M) / (T / M)) / 2

In this manner, each different wavelengths lambda ₁ to [lambda] _M M-number of the fiber grating 23 ₁ ~ 23 _M for reflecting light, at equal intervals of a distance [Delta] L / 2, is provided to the optical fiber 22.

Accordingly, the fiber grating 23 ₁ reflects only light having the wavelength λ ₁ , the fiber grating 23 ₂ reflects only light having the wavelength λ ₂ , the fiber grating 23 ₃ reflects only light having the wavelength λ ₃ , and the fiber grating 23 since _M reflects only light of the wavelength lambda _M, with respect to the wavelength lambda ₁ of light, light of the wavelength lambda ₂ is the time delay of the distance [Delta] L, with respect to the wavelength lambda ₂ of light, light of the wavelength lambda ₃ is The light of the wavelength λ _M is delayed by the time of the distance ΔL with respect to the light of the wavelength λ ₃ , and the optical bits of the wavelengths λ _{1 to} λ _M are sequentially delayed by ΔL. (See FIG. 2 (c)). Thereafter, the optical bits of the wavelengths λ _{1 to} λ _M are recombined, and the optical bits of the wavelengths λ _{1 to} λ _M disappear in time (see FIG. 2D).

  Here, ΔL represents an inter-bit delay when M bits are inserted at equal intervals in an N-bit interval. If the reflected optical bits are separated by the optical circulator 21 and received by the PD 24, The bits of each wavelength can be received independently by the same PD 24. At this time, the transmission rate received by the PD 24 is T / N [bit / s].

  As an example, if T = 100 Gbit / s, M = 4, and N = 16, the transmission speed to be received by the PD 24 is 6.25 Gbit / s, and the operating frequency of a generally inexpensive silicon-based CMOS circuit is 10 GHz or less. It is possible to operate sufficiently.

  Further, when T increases, it is possible to easily reduce the transmission rate to be received by increasing N by that amount.

  Furthermore, ΔL / 2 is about 16 mm because the equivalent refractive index of an optical fiber is about 1.5, and is about 8 mm because the equivalent refractive index of a semiconductor is about 3.2. Then, since the relative dielectric constant is about 4, it is about 12 mm, and it can be sufficiently downsized with any material.

Next, with reference to FIGS. 1A and 1B, a manufacturing method of an optical-optical serial-parallel conversion apparatus for a multi-wavelength optical signal of this reference example will be described. Note that, here, as an example, T = 100 Gbit / s, M = 4, and N = 16.

  First, N (16) optical fibers branched from the 1: N optical splitter 11 are cut and fused so that each optical fiber has a length of 1 bit (here, 25 Gbit / s × 4 wavelengths). 40 ps), specifically, the length is made to be gradually increased by about 8 mm. That is, the length of each optical fiber is a length including each optical delay line 12a.

  Next, the N optical fibers (16 optical fibers) are arranged in a fiber fixing jig in a honeycomb shape excluding the center, aligned with the end face position and the polarization direction, and fixed with a UV adhesive. The fiber array 12 is produced. The output-side fiber array 19 may be configured substantially the same as the input-side fiber array 12, but the configuration is obtained by removing the optical splitter 11 from the input-side fiber array 12, and the optical fiber of the output-side fiber array 19. It is not necessary to set the length of the to be particularly precise.

  A glass microlens array 13a is fixed to the input side surface of the PBS 14 having a cubic structure with a UV adhesive. Each lens of the micro lens array 13a is arranged in the same manner as each optical fiber of the input side fiber array 12 arranged in a honeycomb shape, and converts the light beam emitted from each optical fiber into parallel light. The required numerical aperture is set.

On the surface of the PBS 14 on the surface optical switch 16 side, a triangular 90-degree reflecting mirror 18a made of glass is fixed at its center with a UV adhesive. Further, a collimator fiber 17 having a 90-degree reflection mirror 18b is fixed to the surface of the PBS 14 facing the microlens array 13a with a UV adhesive. As shown in FIG. 1, the collimator fiber 17 and the 90-degree reflecting mirror 18b are arranged so that the control light pulses Pc ₁ and Pc ₂ can be guided to the surface optical switch 16 via the 90-degree reflecting mirror 18a.

  The PBS 14 is fixed to a fixing jig with a UV adhesive, and the input side fiber array 12 is fixed to the input side of the PBS 14 with a UV adhesive at a position corresponding to the focal length of the microlens array 13a. At this time, alignment is performed at an appropriate position while observing parallel light from the surface optical switch 16 side with an infrared camera.

Next, the parallel light from the microlens array 13 a and the control light pulses Pc ₁ and Pc ₂ that have passed through the collimator fiber 17 and the plurality of 90-degree reflection mirrors 18 a and 18 b are collected at one point of the surface optical switch 16. Thus, the position of the aspherical lens 15 is adjusted, and then fixed with a UV adhesive. At this time, the position of the aspherical lens 15 is adjusted to an appropriate position while observing the collected light from the surface optical switch 16 side with an infrared camera.

  Next, the surface type optical switch 16 fixed in advance on the fixed base is disposed at the focal position of the aspheric lens 15. At this time, a ¼ wavelength plate is inserted between the aspherical lens 15 and the PBS 14, and the parallel light from the output side of the PBS 14 is aligned with an appropriate position while observing with an infrared camera.

  Next, after fixing the microlens array 13b with the UV adhesive on the output side surface of the PBS 14, the output side fiber array 19 is aligned at a position that becomes the focal length of the microlens array 13b and fixed with the UV adhesive. To do. At this time, the input light intensity to each fiber of the output side fiber array 19 is observed, and alignment is performed at an appropriate position where they are maximized.

This is the method for manufacturing the serial-parallel converter 10. Next, a manufacturing method of the delay units 20 _{1 to} 20 _N will be described.

In fiber-type delay unit 20 ₁ to 20 _N, first, by using a phase mask method, to prepare a M types of gratings for reflecting different wavelengths lambda ₁ to [lambda] _M in one optical fiber 22, the fiber grating 23 to produce a _{1 ~23 M.} At this time, the relative position of each of the M types of fiber gratings 23 ₁ to 23 _M is set to 16 mm so as to be ΔL / 2 described above. The optical fiber 22 is connected to one output port 21 a of the optical circulator 21.

Next, the optical circulator 21 is connected between the optical fiber 22 and the optical fiber 22 of the output side fiber array 19 of the serial-parallel converter 10, and the light receiving PD 24 is connected to the other output port 21 b of the optical circulator 21. In this manner, the delay unit 20 ₁ to 20 _N is completed.

( Reference Example 2)
In this reference example, N pieces of PLC (planar optical circuit) type delay units 30 shown in FIG. 3 are used instead of the fiber type delay units 20 _{1 to} 20 _N described in the reference example 1. Note that the serial-parallel conversion unit 10, including its configuration, may be manufactured in the same manner as in Reference Example 1, and therefore its illustration and description are omitted here. Also in FIG. 3, the dotted line waveform indicates the signal “0”, and the solid line waveform indicates the signal “1”.

In this reference example, a serial - output side of the parallel converter 10, i.e., each of the output ports P ₁ to P _N of PBS 14, via the output-side fiber array 19, the output from the output port P ₁ to P _N A PLC type delay unit 30 is sequentially connected to each of the optical signals having M wavelengths, which sequentially delays at equal intervals for each wavelength.

The PLC type delay unit 30 is formed on the PLC substrate 32 and is connected to the optical fibers (output ports P _{1 to} P _N ) of the output side fiber array 19 via a circulator 31 described later. If, formed at equal intervals apart from each other on the plane optical waveguide 33 to provide equally spaced delays, and M grating 34 ₁ to 34C _M to reflect light signals of mutually different wavelengths, the output-side fiber array 19 An optical circulator that is inserted between the optical fiber (output ports P _{1 to} P _N ) and the PLC substrate 32 and outputs the optical signals reflected by the _M gratings 34 _{1 to} 34 _M separately from the planar optical waveguide 33. 31. The planar optical waveguide 33 formed on the PLC substrate 32 is connected to one output port 31 a of the circulator 31, and the PD 35 is connected to the other output port 31 b of the circulator 31.

Instead of the gratings 34 _{1 to} 34 _M , M grooves are formed in the planar optical waveguide 33, and multilayer reflection filters for reflecting optical signals of different wavelengths are respectively formed in the formed M grooves. You may make it insert.

Thus, in the delay unit 30 of the PLC type, each different the M grating 34 ₁ to 34C _M for reflecting light having a wavelength lambda ₁ to [lambda] _M, at equal intervals of a distance [Delta] L / 2, the planar optical waveguide 33 Provided.

Therefore, the grating 34 ₁ reflects only the light with the wavelength λ ₁ , the grating 34 ₂ reflects only the light with the wavelength λ ₂ , the grating 34 ₃ reflects only the light with the wavelength λ ₃ , and the grating 34 _M has the wavelength λ _Since only _M light is reflected, light of wavelength λ ₂ is delayed by a time of distance ΔL with respect to light of wavelength λ ₁ , and light of wavelength λ ₃ is time of distance ΔL with respect to light of wavelength λ _2. delayed, with respect to the wavelength lambda ₃ of the light, the light of wavelength lambda _M becomes possible to time delay the distance [Delta] L, light bits of respective wavelengths lambda ₁ to [lambda] _M will be sequentially delayed by [Delta] L ( (Refer FIG.2 (c)). Thereafter, the optical bits of the wavelengths λ _{1 to} λ _M are recombined, and the optical bits of the wavelengths λ _{1 to} λ _M disappear in time (see FIG. 2D). If the reflected optical bits are separated by the optical circulator 31 and received by the PD 35, the bits of each wavelength can be received independently by the same PD 35.

  Next, a method for manufacturing the PLC type delay unit 30 will be described.

In the PLC type delay unit 30, first, the planar optical waveguide 33 is produced on the PLC substrate 32 by using a flame deposition method and a dry etching method. At that time, by using an EB lithography and dry etching, to produce the M types of gratings 34 ₁ to 34C _M to reflect different wavelengths lambda ₁ to [lambda] _M immediately above the planar optical waveguide 33. At this time, the relative position of each of the M types of gratings 34 _{1 to} 34 _M is set to 16 mm so as to be the above-described ΔL / 2.

When a multilayer reflective filter is used in place of the gratings 34 _{1 to} 34 _M , for example, M grooves are cut by a dicing device at positions of ΔL / 2 intervals of the planar optical waveguide 33 to form a groove structure. A reflection filter made in advance with a dielectric multilayer film may be inserted into the created groove structure.

  Next, the optical circulator 31 is connected between the optical fiber of the output side fiber array 19 of the serial-parallel converter 10 and the PLC substrate 32, and the light receiving PD 35 is connected to the other output port 31 b of the optical circulator 31. In this way, the PLC type delay unit 30 is completed.

(Example 1 )
In this embodiment, instead of the delay unit 20 ₁ to 20 _N of the fiber type as described in Reference Example 1, and the delay unit 40 of the stripline shown in FIG. 4 as used N pieces. Note that the serial-parallel conversion unit 10, including its configuration, may be manufactured in the same manner as in Reference Example 1, and therefore its illustration and description are omitted here. In FIG. 4, the dotted waveform indicates the signal “0”, and the solid waveform indicates the signal “1”.

In the present embodiment, the serial - output side of the parallel converter 10, i.e., each of the output ports P ₁ to P _N of PBS 14, via the output-side fiber array 19, the output from the output port P ₁ to P _N Each of the M-wavelength optical signals is separated into wavelengths and converted into electrical signals, and stripline-type delay units 40 are connected to each of the converted electrical signals to sequentially delay at equal intervals.

Delay of stripline 40 is a InP substrate 41, a main optical waveguide 42 connected to the optical fiber on the output side fiber array 19, M-number of gratings 43 formed on the main optical waveguide 42 ₁ ~ 43 _M And coupling waveguides 44 _{1 to} 44 _M coupled to the main optical waveguide 42 by _M gratings 43 ₁ to 43 _M, and waveguide type PD 45 connected to the output end faces of the coupling waveguides 44 _{1 to} 44 _{M. 1 to} 45 _M , ceramic substrate 46, M electrical delay lines 47 _{1 to} 47 _M connected to waveguide type PDs 45 _{1 to} 45 _M , and M electrical delay lines 47 _{1 to} 47 _M Main electrical delay line 48.

The main optical waveguide 42, the gratings 43 ₁ to 43 _M , the coupling waveguides 44 _{1 to} 44 _M, and the waveguide type PDs 45 _{1 to} 45 _M are formed on the InP substrate 41, and the electric delay lines 47 _{1 to} 47 _M and the main electricity The delay line 48 is formed on the ceramic substrate 46, and the waveguide type PDs 45 _{1 to} 45 _M and the electrical delay lines 47 _{1 to} 47 _M are connected by a gold wire.

In this InP substrate 41, M grating couplers are formed in the main optical waveguide 42 by the gratings 43 ₁ to 43 _M and the coupling waveguides 44 _{1 to} 44 _M , and each of the M grating couplers has a different wavelength. Are separated from the main optical waveguide 42 into coupling waveguides 44 _{1 to} 44 _M , respectively. Note that M grating couplers may be formed using another compound semiconductor substrate or PLC substrate instead of the InP substrate 41.

As described above, the stripline type delay unit 40 is provided with M grating couplers that separate light beams having different wavelengths λ _{1 to} λ _M , and further, the optical signals separated by the M grating couplers are respectively electric signals. the M waveguide PD45 ₁ to 45 _M for converting the provided electric signal converted by the waveguide type PD45 ₁ to 45 _M, to provide sequential equally spaced delay for each electric signal, the length of each Electrical delay lines 47 _{1 to} 47 _M that are sequentially increased by ΔL are provided.

Thus, the grating 43 ₁ and coupling waveguide 44 ₁ separates only the light of wavelength lambda _1, a grating 43 _2, and coupling waveguides 44 ₂ separates only the light of wavelength lambda _2, the grating 43 for ₃ and bond The waveguide 44 ₃ separates only light having the wavelength λ ₃ , and the grating 43 _M and the coupling waveguide 44 _M separate only light having the wavelength λ _M. Then, the light of the separated wavelength lambda ₁ is a waveguide type PD45 ₁ is converted into an electric signal, via an electrical delay line 47 ₁ is multiplexed into the main electrical delay line 48, separated wavelength lambda ₂ The light is converted into an electric signal by the waveguide type PD 45 ₂ , and is combined with the main electric delay line 48 and separated through the electric delay line 47 ₂ that is delayed by a distance ΔL with respect to the electric delay line 47 ₁ . the light wavelength lambda _3, the waveguide-type PD45 ₃ is converted into an electric signal, via an electrical delay line 47 ₃ to time delay distance ΔL relative electrical delay line 47 _2, if the main electrical delay line 48 are waves, light separated wavelength lambda _M is converted to an electrical signal by the waveguide PD45 _M, via an electrical delay line 47 _M for time delay distance ΔL relative electrical delay line 47 _3, the main electric It will be multiplexed to the delay line 48. Therefore, the electrical signals corresponding to the wavelengths λ _{1 to} λ _M are sequentially delayed by ΔL, and there is no time overlap.

  Next, a manufacturing method of the stripline type delay unit 40 will be described.

In the stripline type delay unit 40, first, the main optical waveguide 42 and the four coupling waveguides 44 _{1 to} 44 _M are formed on the InP substrate 41 by using a flame deposition method and a dry etching method. At that time, by using the EB drawing method and the dry etching method, M types of gratings 43 ₁ for coupling optical signals having different wavelengths λ _{1 to} λ _M to the coupling waveguides 44 _{1 to} 44 _M immediately above the main optical waveguide 42. Make ~ 43 _M. Thus, optical signals having respective wavelengths lambda ₁ to [lambda] _M is coupled to a different coupling waveguide 44 ₁ ~ 44 _M, it is guided to the output end face of the coupling waveguide 44 ₁ ~ 44 _M. Furthermore, using a dry etching method, the output end face of the coupling waveguide 44 ₁ ~ 44 _M, to form a bench to place a waveguide PD45 ₁ to 45 _M, the PD45 ₁ to 45 _M thereon with solder bumps Fix it.

Further, a ceramic substrate 46 having four electric delay lines 47 _{1 to} 47 _M and a main electric delay line 48 for multiplexing them is prepared, and the four electric delay lines 47 _{1 to} 47 _M and each PD 45 _{1 are} prepared. Connect ~ 45 _M with gold wire. The four delay lines have the aforementioned ΔL / 2 of 12 mm so that the respective signals are sequentially delayed at equal intervals in time. In this way, the stripline type delay unit 40 is completed.

  The present invention is suitable for optical communication of multi-wavelength optical packets.

10 Serial - parallel converter 20 ₁ to 20 _N delay unit 21 the optical circulator 22 optical fibers 23 ₁ ~ 23 _M fiber grating 24 PD
30 delay unit 31 optical circulator 32 PLC substrate 33 planar optical waveguide 34 _{1 to} 34 _M grating 35 PD
40 delay section 41 InP substrate 42 main waveguide 43 ₁ to 43 _M grating 44 _{1 to} 44 _M coupling waveguide 45 _{1 to} 45 _M waveguide type PD
46 Ceramic substrate 45 _{1 to} 45 _M electrical delay line 48 main electrical delay line

Claims (1)

Light of a multi-wavelength optical signal, which is composed of optical signals of M wavelengths having the same transmission speed and serial-parallel converts 1: N into a multi-wavelength optical signal in which the first bits of the M optical signals are aligned at the same time. An optical serial-parallel converter,
A serial-parallel converter that outputs each bit to N output ports at different positions for every N bits of the multi-wavelength optical signal, and performs serial-parallel conversion to 1: N;
A delay unit connected to each of the output ports, separating optical signals having M wavelengths output from the output ports for each wavelength, converting the optical signals into electrical signals, and sequentially delaying the electrical signals at equal intervals It has a door,
The serial-parallel converter is
A demultiplexer for demultiplexing the multi-wavelength optical signal into N parallel optical signals;
An optical delay unit that sequentially delays each of the N parallel optical signals demultiplexed by the demultiplexer by 1 bit;
A polarized beam that reflects the N parallel optical signals delayed by the optical delay unit, transmits an optical signal having a polarization direction different from that of the N parallel optical signals, and outputs the optical signal to the N output ports. A splitter,
A lens that condenses the N parallel optical signals reflected by the polarization beam splitter at one point;
An optical switch that is arranged at one point condensed by the lens and changes the polarization direction of the N parallel optical signals collected and reflects to the polarization beam splitter while a predetermined optical pulse is being input. When,
An optical pulse that outputs the predetermined optical pulse at a timing at which the first to Nth bits of the N parallel optical signals sequentially delayed one bit at a time by the optical delay unit are condensed on the optical switch. A generator,
The delay unit is
An optical waveguide connected to the output port and formed on a planar optical circuit substrate or a compound semiconductor substrate;
M grating couplers formed in the optical waveguide and separating optical signals of different wavelengths,
M photodiodes each converting the optical signal separated by the grating coupler into the electrical signal;
M electrical delay lines for sequentially delaying the electrical light signals converted by the photodiodes at equal intervals for each electrical signal;
An optical-optical serial-parallel conversion of a multi-wavelength optical signal, comprising: a main electrical delay line connected to the M electrical delay lines and configured to multiplex the delayed electrical signals apparatus.
However, M and N are natural numbers of 2 or more.