JP6110718B2 - Optical signal processing circuit - Google Patents

Description

  The present invention relates to an optical signal processing circuit, and more particularly to a signal processing circuit capable of performing a time-space conversion signal processing and a wavelength multiplexing by a plurality of high-speed optical signal units collectively.

  With the development of optical signal transmission technology and optical signal processing technology, it has become necessary to handle high-speed and large-capacity optical signals. However, when the signal speed is increased, there is a problem that electrical processing becomes extremely difficult when performing signal processing. For this reason, a spatio-temporal conversion signal processing (see Non-Patent Document 1) that can perform signal processing of a high-speed optical signal as light is attracting attention. First, the time waveform is converted into a time waveform using a dispersion element such as a diffraction grating or an arrayed waveguide grating (AWG), and the time waveform is subjected to Fourier transform using a lens or the like, whereby the time frequency spectrum of the time waveform is converted. Is converted to a spatial frequency spectrum. Then, the spatial frequency spectrum is filtered by a spatial filter capable of spatially modulating the intensity and phase, and then converted into a time waveform again by performing the reverse process. Thereby, optical signal processing can be performed on the time waveform of the ultrafast optical signal.

  Since this optical signal processing method uses AWG or the like used for multiplexing / demultiplexing of wavelength division multiplexing (WDM) optical signals as dispersion elements, it is possible to perform batch signal processing on WDM signals in parallel. Has the advantage.

T. Kurokawa, et al., “Time-space-conversion optical signal processing using arrayed-waveguide grating,” Electronics Letters, 1997, Vol. 33, No. 22, pp.1890-1891

  However, the conventional space-time conversion optical signal processing circuit using AWG has a problem that the input port and the output port are the same. When space-time converted optical signal processing is performed on a signal that has already been WDM, signal processing can be performed in a lump without problems with a conventional optical signal processing circuit. On the other hand, for example, there is a problem that the apparatus becomes complicated in order to generate a special transmission optical signal such as an optical single sideband (SSB) signal and an optical Nyquist pulse that are wavelength-multiplexed when transmitting a WDM signal.

  FIG. 9 shows a configuration of a conventional optical signal processing circuit. Wavelength multiplexing processing for generating a WDM signal is performed in a front stage portion composed of a plurality of input waveguides 901, slab waveguides 902, arrayed waveguides 903, and slab waveguides 904 that receive signal light of wavelengths λ1 to λ4. After that, the focal points of the single input waveguide 906, the slab waveguide 907, the arrayed waveguide 908, the slab waveguide 909, and the slab waveguide 909, which are connected to the front stage through the optical circulator 905 and receive the WDM signal. Spatio-temporal conversion optical signal processing is performed in the rear stage part composed of the reflective spatial filter 910 arranged on the surface. Thus, it is necessary to separately prepare a circuit for performing wavelength multiplexing processing and a circuit for performing space-time conversion optical signal processing, and the combination of them complicates the apparatus.

  The present invention has been made in view of such problems, and an object of the present invention is to perform space-time conversion optical signal processing on optical signals having different wavelengths input from a plurality of ports, and to perform wavelength multiplexing. An object of the present invention is to provide a simple space-time conversion optical signal processing circuit capable of performing processing with one AWG.

In order to solve the above problems, the present invention is an optical signal processing circuit, wherein a first slab waveguide and a second slab waveguide are connected by an arrayed waveguide, and a plurality of input waveguides are provided. And an arrayed waveguide grating in which at least one output waveguide adjacent to the input waveguide is connected to the first slab waveguide, and a spatial filter disposed in the vicinity of the focal plane of the second slab waveguide A spatial filter having a phase modulation structure for reflecting and coupling optical signals incident from the plurality of input waveguides to the output waveguide , wherein the phase modulation structure comprises the second modulation structure. A resist laminated on a substrate having an inclined surface having a phase delay amount corresponding to a positional relationship with the output waveguide for each incident position of an optical signal in which a frequency component is spatially expanded in a slab waveguide; Laminated on the inclined surface Characterized in that a laminated structure of a metal film.

2. The optical signal processing circuit according to claim 1 , wherein the phase modulation structure has the metal film laminated on the entire surface of the inclined surface.

The invention according to claim 3, in the optical signal processing circuit according to claim 1, wherein the phase modulation structure, for each of the inclined surface, the metal to reflect only one side of the sideband of the optical signal A film is laminated on a part of the inclined surface, and a non-reflective film is laminated on a part of the inclined surface so as to absorb one sideband.

The invention according to claim 4, the optical signal processing circuit according to claim 1, wherein the phase modulation structure, the each inclined surface of the inclined surface only such that the reflection center of the spectrum of the optical signal one The metal film is laminated on the portion.

According to a fifth aspect of the present invention, in the optical signal processing circuit according to any one of the first to fourth aspects, the arrayed waveguide grating is formed of a quartz waveguide.

  In the present invention, a spatio-temporal conversion optical signal processing circuit can be simplified by performing spatio-temporal conversion optical signal processing on optical signals having different wavelengths input from a plurality of ports and performing wavelength multiplexing processing with one AWG. Can be

It is a figure which shows the structure of the optical signal processing circuit which concerns on one Embodiment of this invention. (A) is a figure which shows the electric field amplitude in the focal plane of the output light from a slab waveguide, (b) is a figure which shows the phase in the focal plane of the output light from a slab waveguide. (A) is a figure which shows the electric field amplitude in the focal plane of the output light from a slab waveguide, (b) is a figure which shows the phase in the focal plane of the output light from a slab waveguide. (A) is a figure which shows the structure of the spatial filter which concerns on one Embodiment of this invention, (b) is a figure which shows the phase delay amount given by the spatial filter, (c) is given by the spatial filter It is a figure which shows the phase of the reflected electric field produced. (A) is a figure which shows the structure of the spatial filter for SSB signals for producing | generating the SSB signal which concerns on one Embodiment of this invention, (b) is a figure which shows the phase delay amount given by the spatial filter (C) is a figure which shows the phase of the reflected electric field given by the spatial filter. (A) is a figure which shows the electric field amplitude after filtering by the spatial filter for SSB signals, (b) is a figure which shows the phase after filtering by the spatial filter for SSB signals. It is a figure which shows the structure of the spatial filter for optical Nyquist pulses for producing | generating the optical Nyquist pulse which concerns on one Embodiment of this invention, is a figure which shows the phase delay amount given by the spatial filter 105, and shows the phase of a reflected electric field. FIG. (A) is a figure which shows the electric field amplitude after filtering by the optical Nyquist pulse spatial filter, (b) is a figure which shows the phase after filtering by the optical Nyquist pulse spatial filter. It is a figure which shows the structure of the conventional optical signal processing circuit.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 shows a configuration of an optical signal processing circuit according to an embodiment of the present invention. Signal light having wavelengths λ1 to λ4 incident from the plurality of input waveguides 101 is distributed to each waveguide of the arrayed waveguide 103 by the slab waveguide 102. Each output light from the arrayed waveguide 103 is collected by the slab waveguide 104. The array waveguide 103 has a function of time-space converting incident signal light, and the slab waveguide 104 has a function of Fourier transforming each output light from the array waveguide 103. That is, the frequency component of the input optical signal is spatially developed on the end face (focal plane) opposite to the end face connected to the arrayed waveguide 103 of the slab waveguide 104, and the spatial axis and the frequency axis are linear. They are proportional to each other through dispersion. A circuit configuration including the input waveguide 101, the slab waveguide 102, the arrayed waveguide 103, and the slab waveguide 104 is generally called an arrayed waveguide grating (AWG).

  A reflective spatial filter 105 is disposed on the focal plane of the slab waveguide 104, and intensity and phase modulation can be applied to an input optical signal (optical spectrum) in which frequency components are spatially expanded.

  The center wavelength of the arrayed waveguide 103 used in this embodiment is 1552 nm, the number thereof is 378, and the diffraction order (the value obtained by dividing the optical path length difference between adjacent waveguides by the wavelength) is 327. The linear dispersion at the focal plane of the slab waveguide 104 is 250 MHz / μm, and the frequency resolution is about 2.2 GHz. The number of the plurality of input waveguides 101 is four, and the input waveguides 101 are designed to enter the slab waveguide 102 at intervals equivalent to 200 GHz intervals.

  The optical signal processing circuit of FIG. 1 may be a silica-based optical waveguide manufactured as follows. That is, after depositing as a glass fine particle film in the order of the lower cladding layer and the core layer on the single crystal silicon substrate by the flame hydrolysis volume method (FHD method), it is heated to a high temperature in an annealing furnace to cover the silicon substrate. A transparent glass film is used. Then, after patterning the waveguide, using dry etching to remove the unnecessary core layer, the upper cladding layer is deposited again using the FHD method, and heated to a high temperature to make the upper cladding layer transparent. Let

  In the present invention, in addition to the silica-based optical waveguide, a semiconductor waveguide structure produced by epitaxially growing a semiconductor having a refractive index higher than that of a cladding such as InGaAsP as a core layer on a semiconductor layer such as InP, and patterning and etching. Alternatively, a waveguide structure made of a polymer in which the core is deuterated PMMA and the cladding is an ultraviolet curable resin may be used. In this case, it is desirable that the material is sufficiently transparent in the wavelength range to be used.

  Here, the electric field on the focal plane of the slab waveguide 104 when light of frequencies λ1, λ2, λ3, and λ4 having a frequency interval of 100 GHz is incident from four input waveguides will be described. Since the interval between the incident waveguides is 200 GHz, the optical spectrum of λ1, λ2, λ3, and λ4 is developed on the focal plane of the slab waveguide 104 at intervals corresponding to 100 GHz intervals (400 μm in this embodiment). . 2A and 2B show the electric field amplitude and phase at this time.

  Here, as shown in FIG. 3, the wavefront of the reflected spatial frequency spectrum can be controlled by tilting the phase of each incident spectrum with respect to the spatial position. Specifically, by independently controlling the phase to be given to the optical spectrum of the frequencies λ1, λ2, λ3, and λ4, the optical signal reflected by the spatial filter 105 is not the original input waveguide 101, It becomes possible to multiplex and output to one output waveguide 106. As a result, it has become possible to perform space-time conversion optical signal processing and wavelength multiplexing processing, which have been performed independently by two AWGs, by one AWG.

  4A to 4C show the detailed structure of the spatial filter 105, the phase delay amount provided by the spatial filter 105, and the phase of the reflected electric field. The spatial filter 105 has a phase modulation structure including an electron beam drawing resist 402 and a gold mirror 403 at each position where the optical spectrum of the frequencies λ1, λ2, λ3, and λ4 on the filter substrate 401 made of quartz is developed. Yes. This was produced as follows.

  Patterning with a resist on the filter substrate 401, spatially adjusting the dose (charge implantation) with an electron beam lithography system, exposing and developing after a certain period of time, so that the inclination varies depending on the position where the optical spectrum is developed. Can be formed. Thereafter, a gold mirror 403 was deposited on the entire surface of the electron beam drawing resist 402 by 200 μm.

  When an optical signal (wavelengths of 155.15 nm, 1552.9 nm, 1553.7 nm, and 1554.5 nm, respectively) is actually incident using the spatial filter 105 shown in FIG. 4A, all four wavelengths are output. It was confirmed that the light was emitted from the port 106.

  In the above example, since the gold mirror 403 is deposited on the entire surface, the entire spectrum is reflected by the spatial filter 105, but signal processing can be performed by patterning the gold mirror 403.

  5A to 5C show the structure of an SSB signal spatial filter for generating an SSB signal according to an embodiment of the present invention, the phase delay amount provided by the spatial filter 105, and the phase of the reflected electric field. . FIGS. 6A and 6B show the electric field amplitude and phase after filtering by the SSB signal spatial filter. Since only one sideband of the carrier wave is reflected and the other sideband is cut (absorbed) by the non-reflective film 501, the optical spectrum after filtering becomes an optical SSB signal.

  FIG. 7 shows the structure of an optical Nyquist pulse spatial filter for generating an optical Nyquist pulse according to an embodiment of the present invention, the phase delay amount provided by the spatial filter 105, and the phase of the reflected electric field. 8A and 8B show the electric field amplitude and phase after filtering by the optical Nyquist pulse spatial filter. An optical Nyquist pulse is formed by patterning the gold mirror 403 so as to reflect only the center of the spectrum as shown in FIG. 7A to form a spectrum as shown in FIG. Can also be generated.

  In this embodiment, the spatial filter 105 is formed on the filter substrate 401 with the electron beam drawing resist 402, the gold mirror 403, and the non-reflective film 501, but a reflective surface is dynamically configured such as LCOS (Liquid crystal on silicon). A possible spatial filter 105 may be used.

  As described above, in the space-time conversion optical signal processing circuit of the present invention, by providing a wavefront control structure in a spatial filter, a single AWG can handle a plurality of optical signals having different wavelengths input from a plurality of ports. In addition, the space-time conversion optical signal processing can be performed individually, and wavelength multiplexing processing can also be performed.

101, 901 Input waveguide 102, 104, 902, 904, 907, 909 Slab waveguide 103, 903, 908 Array waveguide 105, 910 Spatial filter 106 Output waveguide 401 Filter substrate 402 Electron beam drawing resist 403 Gold mirror 501 None Reflective film 905 Optical circulator 906 Input / output waveguide

Claims (5)

The first slab waveguide and the second slab waveguide are connected by an arrayed waveguide, and a plurality of input waveguides and at least one output waveguide adjacent to the input waveguide are the first slab waveguide. An arrayed waveguide grating connected to the waveguide;
A spatial filter disposed in the vicinity of a focal plane of the second slab waveguide, and having a phase modulation structure for reflecting an optical signal incident from the plurality of input waveguides to couple to the output waveguide A spatial filter,
The phase modulation structure has a phase delay amount corresponding to the positional relationship with the output waveguide for each incident position of the optical signal in which the frequency component is spatially expanded in the second slab waveguide. An optical signal processing circuit comprising a laminated structure of a resist laminated on a substrate having an inclined surface and a metal film laminated on the inclined surface.   The optical signal processing circuit according to claim 1, wherein the phase modulation structure has the metal film laminated on the entire inclined surface.   In the phase modulation structure, for each inclined surface, the metal film is laminated on a part of the inclined surface so as to reflect only one side band of the optical signal, and absorbs one side band. The optical signal processing circuit according to claim 1, wherein an antireflective film is laminated on a part of the inclined surface.   2. The phase modulation structure according to claim 1, wherein the metal film is laminated on a part of the inclined surface so that only the center of the spectrum of the optical signal is reflected for each inclined surface. Optical signal processing circuit. The arrayed waveguide grating, the optical signal processing circuit according to any one of claims 1 to 4, characterized in that it is formed of quartz waveguide.

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