JP6251206B2 - Optical transmission / reception system - Google Patents

Description

  The present invention relates to a configuration of an optical transmission / reception system using an optical module mainly applied to optical fiber communication. More particularly, the present invention relates to an optical transmission / reception system for performing telecom and datacom transmission using wavelength division multiplexing communication and a configuration of an optical circuit thereof.

  In recent years, the remarkable progress of optical fiber communication technology, particularly the data link market represented by communication between data centers, has dramatically increased the throughput of optical links. Currently, in the standard for a transmission distance of 10 km in 100 Gigabit Ethernet (registered trademark) (100 GbE), a configuration using wavelength division multiplexing (WDM) transmission using a single mode fiber is specified (25 Gb / wave per wave). s baud rate). In the future, the 400 Gigabit Ethernet (400 GbE) standard is drawing attention as a next-generation configuration for expanding the transmission capacity, and proposals for the physical configuration are being actively made at present.

  A frequency arrangement called LAN-WDM is applied to four-wave WDM transmission in the 10 GbE 10 km transmission specification. That is, the arrangement is four waves with a frequency interval ΔF of 800 GHz, and the use band (passband) B in each wavelength (lane) is 360 GHz. The center wavelength of each lane is designated as 129.56 nm for lane 0, 1300.05 nm for lane 1, 1304.58 nm for lane 2, and 1309.14 nm for lane 3. The total number of fiber cores is one for transmission and two for reception.

  On the other hand, in a PON (Passive Optical Network) of a wide area Ethernet line or a high-speed optical access system introduced for private line communication for enterprises, a single-core fiber, that is, a system configuration for both transmission and reception is used. The main method for realizing single-core bidirectional communication by full-duplex communication (no time-division duplex in transmission and reception) is to provide nonreciprocal circuits such as circulators and isolators in the optical link of each terminal station. And a technique based on wavelength multiplexing using different wavelengths for transmission and reception (see, for example, FIG. 4 of Patent Document 1). When the former nonreciprocal circuit is used, there is an economic advantage that the same optical wavelength can be used for transmission and reception, but the quality fluctuation due to reflected return light in the link and scattered light (such as stimulated Brillouin scattering) in the optical fiber Therefore, it is necessary to take measures such as suppressing the maximum optical output (shortening the transmission distance). The latter, that is, a system that performs wavelength multiplexing communication, is less susceptible to the effects of return light and scattering, and thus allows flexible system design, but requires a light source, light receiving element, wavelength filter, etc. to accommodate various wavelengths. Therefore, sharing parts as much as possible is important for economy. Hereinafter, this application is a proposal regarding single-core multiplexing using wavelength division multiplexing.

FIG. 12 shows a conventional single-core bidirectional transmission configuration using an interleave filter disclosed in FIG. 11 of Patent Document 1. This optical transmission / reception system includes first, third, fifth, and seventh downstream optical signal transmitters 111 ₁ , 111 ₃ , 111 _5, and 11 ₇ that transmit downstream optical signals, and these first, third, and _third optical transmitters. Downlinks for multiplexing the downstream optical signals of odd-numbered wavelengths λ ₁ , λ ₃ , λ _5, and λ ₇ sent from the fifth and seventh downstream optical signal transmitters 111 ₁ , 111 ₃ , 111 _5, and 11 ₁₇ , respectively. The optical multiplexer for signal multiplexing 601 and the downstream optical signals of the odd-numbered wavelengths λ ₁ , λ ₃ , λ _5, and λ ₇ combined by the optical multiplexer for downstream signal multiplexing 601 are divided into the even channel and the odd channel. Downlink signal demultiplexing demultiplexer receiving and demultiplexing from the first uplink / downlink signal combining / separating optical interleaver 301 via the optical fiber transmission line 113 and the second uplink / downlink signal combining / separating optical interleaver 302 602 and downlink signal demultiplexing Odd-numbered wavelength lambda ₁ by the demultiplexer 602 is demultiplexed, lambda _3, first for receiving a downstream optical signal of lambda ₅ and lambda _7, third, fifth and seventh optical signal receiver 115 _1, 115 _3, 115 ₅ and 115 _7, the second, fourth, sixth and eighth upward optical signal transmitter 116 _2, 116 _4, 116 _6, and 116 ₈ for transmitting the even-numbered upstream optical signals, these second, fourth, sixth and eighth upward optical signal transmitter 116 ₂ of 116 _4, 116 _6, and 116 ₈ even-numbered wavelength lambda ₂ fed respectively from, lambda _4, upstream of the lambda ₆ and lambda ₈ Uplink signal multiplexing optical multiplexer 603 that multiplexes optical signals, and even-numbered upstream optical signals of wavelengths λ ₂ , λ ₄ , λ _6, and λ ₈ multiplexed by this uplink signal multiplexing optical multiplexer 603 , A second uplink / downlink signal optical separation / separation for separating even and odd channels Uplink signal demultiplexing demultiplexer 604 that receives and demultiplexes from tallyer 302 via optical fiber transmission line 113 and first uplink / downlink signal combining / separating optical interleaver 301, and uplink signal demultiplexing demultiplexer 604. , _Second , _fourth , _sixth and _eighth upstream optical signal receivers 117 ₂ , 117 ₄ , which receive the upstream optical signals of even-numbered wavelengths λ ₂ , λ ₄ , λ ₆ and λ ₈ separated by 117 ₆ and 117 ₈ . This conventional example includes a first wavelength group 312 including four wavelengths (λ ₁ , λ ₃ , λ _5, and λ ₇ ) of the downstream optical signal and four wavelengths (λ ₂ , λ ₄ , λ _6, and λ) of the upstream optical signal. The second wavelength group 313 including ₈ ) is combined to function as a bidirectional system. If the transmission rate of each wavelength is 10 Gbps for both upstream and downstream, a bidirectional system having a total transmission capacity of 40 Gbps is obtained.

  The optical interleavers 301 and 302 for uplink / downlink signal interleaving, for example, interleave wavelength multiplexed (WDM) signals at intervals of 400 GHz at intervals of 800 GHz, or the first wavelength group 312 and the first wavelength group 312 at intervals of 800 GHz. And wavelength-division multiplexing (WDM) the second wavelength group 313 at intervals of 800 GHz and shifted by 400 GHz at intervals of 400 GHz.

FIG. 13 shows the relationship between the signal wavelength and the transmission characteristics of the downlink signal multiplexing optical multiplexer, the uplink signal multiplexing optical multiplexer, the downlink signal demultiplexing duplexer, and the uplink signal demultiplexing duplexer. It is a thing. The transmission characteristics of the optical multiplexer 601 for downlink signal multiplexing and the splitter 602 for downlink signal demultiplexing are the same, and the transmission characteristics are as shown by the broken line 611 for the wavelength λ ₁ , and for the wavelength λ ₃ . Has a transmission characteristic as indicated by a broken line 613. In the following, transmission characteristics are indicated by a broken line 615 for the wavelength λ _{5 and} a broken line 617 for the wavelength λ ₇ , respectively. Also for the uplink signal multiplexing optical multiplexer 603 and the uplink signal demultiplexing demultiplexer 604, the broken line 612 for the wavelength λ ₂ , the broken line 614 for the wavelength λ ₄ , and the broken line 616 for the wavelength λ ₆ . The transmission characteristic is as indicated by a broken line 618 with respect to the wavelength λ ₈ .

  Although not shown, Patent Document 1 also discloses a single-core bidirectional optical transmission / reception system using a circulator instead of an interleaver (FIG. 10 of Patent Document 1).

Further, a single-core bidirectional optical wavelength division multiplexing transmission system using an arrayed waveguide diffraction grating (AWG) having periodicity as an optical filter for wavelength multiplexing is known (see the drawing of Patent Document 2). The AWG periodicity is, for example, when an AWG having a 1 × 4 input / output end is used as a demultiplexer, wavelengths λ ₁ , λ ₂ , λ ₃ and λ ₄ (provided that λ ₁ < λ ₂ <λ ₃ <λ ₄ ) and these wavelengths λ ₁ , λ ₂ , λ _3, and λ ₄ respectively have the same wavelength interval, that is, wavelengths λ ₁₁ , λ that have a circular wavelength relationship. _When optical signals of ₁₂ , λ ₁₃ and λ ₁₄ (where λ ₁₁ <λ ₁₂ <λ ₁₃ <λ ₁₄ ) are input, the wavelength λ ₁ from each output end (port) 1, 2, 3 and 4 side, respectively. , Λ ₂ , λ _3, and λ ₄ in addition to the optical signals that can pass through the same output terminals (ports) 1, 2, 3, and 4, these wavelengths λ ₁ , Wavelengths λ ₁₁ , λ ₁₂ , λ _13, and λ ₁ that are at the same wavelength intervals as the optical signals of λ ₂ , λ _3, and λ ₄ , that is, have a circular wavelength relationship. _This means a filter function that can output an optical signal of ₄ (wavelength λ ₁ and wavelength λ ₁₁ are output from output end 1, wavelength λ ₂ and wavelength λ ₁₂ are output from output end 2, and output end 3 outputs a wavelength λ ₃ and a wavelength λ ₁₃ , and outputs an output end 4 outputs a wavelength λ ₄ and a wavelength λ ₁₄ .

JP2003-283438 JP 2003-143084 A

  In the optical transmission / reception system and optical circuit of Patent Document 1 shown in FIG. 12, the wavelength demultiplexing elements (602, 604) on the receiving side have different filter characteristics (FIG. 13), and therefore different filters are separately prepared at both terminal stations. There is a need to. Therefore, there is a problem that not only the part cost increases due to the increase in the part type, but also an increase in operation for distinguishing the type at the time of system construction and an increase in connection mistakes. For example, when demultiplexing a WDM signal having an interval of 100 GHz into a WDM signal having a frequency interval of 400 GHz, a two-stage interleave filter is used. Further, when each interleave filter is formed of a spatial optical system component such as a dielectric multilayer film or a circulator, there is a problem that the configuration of the optical multiplexing / demultiplexing system and the optical circuit is complicated and large.

  Although it is conceivable to reduce the size by using a PLC that is a planar optical circuit as the interleave filter, there is a limit to downsizing the chip size because a multi-stage Mach-Zehnder circuit is used.

  Further, in the single-core bidirectional optical transmission / reception system described in Patent Document 1 using a circulator instead of an interleaver, it is possible to make the wavelength band of the upstream signal and downstream signal the same, thus simplifying the system. On the other hand, while the cost can be improved, the signal quality is inevitably deteriorated due to Brillouin scattering in the fiber. Therefore, there is a problem that transmission at a high light output in which the scattering intensity increases is difficult and long-distance transmission is not possible. In order to avoid the same problem, the system of Patent Document 1 is limited to use below the threshold for Brillouin scattering.

  In Patent Document 2, although periodic AWG is used, an optical coupler is used in a terminal station (relay station and subscriber's house) to separate an optical transmitter and an optical receiver, that is, to make it bidirectional. Therefore, in addition to the necessity of installing an isolator having a high non-reciprocal circuit in the optical transmitter, there is a problem that an excess loss of 50% (3 dB) is generated by the optical coupler.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a compact, simple, and economical single-core bidirectional optical transmission / reception system and an optical circuit thereof. It is.

  In order to achieve such an object, one aspect of the present invention is an M channel wavelength multiplexed light obtained by combining N sets of M channel multi-wavelength light sources having a frequency interval ΔF and the M channel. / N sets of M-channel wavelength multiplexed light from each of the two sets of multi-wavelength light sources are combined with the first M × N / 2-channel wavelength multiplexed light, and the second M × N / 2-channel wavelength A first periodic wavelength multiplexing / demultiplexing element that demultiplexes the multiplexed light into N / 2 sets of M channel wavelength multiplexed lights, and another N / 2 sets of multiwavelength light sources among the N sets of multiwavelength light sources. N / 2 sets of M channel wavelength multiplexed light from each are combined with the second M × N / 2 channel wavelength multiplexed light, and the first M × N / 2 channel wavelength multiplexed light is combined with the N / N A second periodic wavelength multiplexing / demultiplexing element that demultiplexes two sets of M-channel wavelength multiplexed light, and the first periodic wavelength multiplexing / demultiplexing element. N / 2 sets of multi-wavelength light receiving elements that receive N / 2 sets of split M-channel multi-wavelength light and N / 2 sets of M split by the second periodic wavelength multiplexing / demultiplexing element. And N / 2 sets of multi-wavelength light receiving elements that receive channel multi-wavelength light, and connects the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. An optical transmission / reception system for transmitting and receiving the first M × N / 2 channel wavelength-multiplexed light and the second M × N / 2 channel wavelength-multiplexed light using a single fiber.

  In one embodiment, the period of the first periodic wavelength multiplexing / demultiplexing element and the period of the second periodic wavelength multiplexing / demultiplexing element are configured to be equal to the frequency interval ΔF of the multi-wavelength light source.

  In one embodiment, in the M-channel multi-wavelength light source, the frequency of adjacent sets is shifted by Δf as a whole, and N sets of interval products Δf × (N−1) are the wavelength components in the multi-wavelength light receiving element. It is smaller than the transmission band B of the wave element. The M-channel multi-wavelength light source has N sets of interval products Δf × (N−1) within 600 GHz.

  In one embodiment, the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are arrayed waveguide gratings. The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are the same. The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element have a port interval Δf, and the product of the port intervals Δf × (N−1) is the first periodicity. It is half or less of the periodicity ΔF of the wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element.

  In one embodiment, the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element include N input / output channel waveguides for inputting M-channel wavelength multiplexed light, and the N An input / output slab waveguide connected to the input / output channel waveguide and the wavelength of the M-channel wavelength multiplexed light connected to the input / output slab waveguide together with the N input / output channel waveguides. A wavelength-division slab waveguide connected to the input / output slab waveguide and the array waveguide, a wavelength-division waveguide connected to the wavelength-division slab waveguide, and the wavelength-division slab waveguide A loop-back waveguide connected to the waveguide together with the wavelength multiplexing waveguide for re-inputting part of the output M × N / 2-channel wavelength multiplexing light to the wavelength multiplexing slab waveguide. The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element extract a part of the M × N / 2-channel wavelength multiplexed light to which the wavelength multiplexing waveguide is connected. A tap circuit is provided, and a part of the extracted M × N / 2 channel wavelength division multiplexed light is connected to the loopback waveguide.

  As described above, according to the optical transmission / reception system of one aspect of the present invention, there are N sets of M-channel multi-wavelength light sources having a frequency interval ΔF, and N / 2 sets of M-channel wavelength multiplexed light are the first. The first periodic wavelength multiplexing / demultiplexing that multiplexes the M × N / 2 channel wavelength multiplexed light and demultiplexes the second M × N / 2 channel wavelength multiplexed light into N / 2 sets of M channel wavelength multiplexed light. The element and the other M / 2 sets of M channel wavelength multiplexed light are combined with the second M × N channel wavelength multiplexed light into N sets of M channel wavelength multiplexed light to obtain the first M × N / 2 channel wavelength. A second periodic wavelength multiplexing / demultiplexing element that demultiplexes the multiplexed light into N / 2 sets of M channel wavelength multiplexed light, and N sets (2 × N / 2), the first periodic wavelength multiplexing / de-multiplexing element In addition, by setting the period of each of the second periodic wavelength multiplexing / demultiplexing elements to a condition equal to the frequency interval ΔF of the multi-wavelength light source, an existing WDM system can have a higher density and higher bit rate with a simple configuration. Expansion to a core bidirectional optical transmission / reception WDM becomes possible.

  Furthermore, in the optical transmission / reception system of one embodiment of the present invention, since N sets of interval products Δf × (N−1) are smaller than the transmission band B of the wavelength demultiplexing element in the multiwavelength light receiving element, each multiwavelength light receiving element has a wavelength component. It is possible to use the same parts including wave characteristics. Therefore, the system can be further simplified and made economical.

  In the optical transmission / reception system of one embodiment of the present invention, since the M channel multi-wavelength light sources have N sets of interval products Δf × (N−1) within 600 GHz, each multi-wavelength light source has an oscillation wavelength characteristic of the light source. The same parts can be used. Therefore, the system can be further simplified and made economical.

  In the optical transmission / reception system of one aspect of the present invention, a PLC type arrayed waveguide diffraction grating (AWG) is applied to the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. As a result, an optical circuit that is smaller and simpler than the conventional interleave type filter can be realized.

  In the optical transmission / reception system of one embodiment of the present invention, the product Δf × (N−1) is the period of the port interval Δf between the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. It was set to 1/2 or less of the property ΔF. As a result, as shown in the result of FIG. 5, the wavelength used can be near the center in the FSR, so that an optical circuit with low loss characteristics can be realized.

  Further, in the optical transmission / reception system of one aspect of the present invention, the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are made the same, thereby further reducing the size and economy of the optical circuit. It is feasible.

  In the optical transmission / reception system of one embodiment of the present invention, a monitor waveguide and a loopback waveguide are added to the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. Since it can be added without deteriorating, the monitoring function of the wavelength and light intensity of each multi-wavelength light source can be realized with a small and simple configuration.

  In the optical transmission / reception system of one embodiment of the present invention, the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are further integrated by integrating tap circuits on the same substrate. Can be reduced in size and economy.

It is a block diagram of the optical transmission / reception system concerning one Embodiment of this invention. It is a figure which shows wavelength arrangement | positioning of the optical transmission / reception system concerning one Embodiment of this invention. It is a block diagram of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning one Embodiment of this invention. It is a block diagram of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning one Embodiment of this invention. It is a figure which shows the transmission spectrum of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning one Embodiment of this invention. It is a figure which shows wavelength arrangement | positioning of the multiwavelength light source concerning one Embodiment of this invention. It is a figure which shows the output spectrum from the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning one Embodiment of this invention. It is a block diagram of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning 2 embodiment of this invention. It is a block diagram of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning 2 embodiment of this invention. It is a block diagram of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning 3 embodiment of this invention. It is a figure which shows the transmission spectrum of the 1st periodic wavelength multiplexing / demultiplexing element and the 2nd periodic wavelength multiplexing / demultiplexing element in the optical transmission / reception system concerning 3 embodiment of this invention. It is a figure which shows the structure in the conventional optical transmission / reception system. It is a figure which shows the wavelength arrangement | positioning in the conventional optical transmission / reception system.

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

(First embodiment)
With reference to FIGS. 1 to 7, an optical transmission / reception system and an optical circuit thereof according to a first embodiment of the present invention will be described.
FIG. 1 is a configuration diagram of an optical transmission / reception system 100 of the present embodiment. In this system, N sets (110-1 to 110-N) of M-channel multi-wavelength light sources having a frequency interval ΔF and N / 2 sets of M-channel wavelength multiplexed light to the first M × N / 2-channel wavelength A first periodic wavelength multiplexing / demultiplexing element 130 that multiplexes the multiplexed light and demultiplexes the second M × N / 2 channel wavelength multiplexed light into N / 2 sets of M channel wavelength multiplexed light; Two sets of M channel wavelength multiplexed light are combined with the second M × N / 2 channel wavelength multiplexed light, and the first M × N / 2 channel wavelength multiplexed light is combined with N / 2 sets of M channel wavelength multiplexed light. A second periodic wavelength multiplexing / demultiplexing element 140 that demultiplexes the first M × N / 2-channel wavelength multiplexed light into N / two sets of M-channel multi-wavelength light. Two sets (152-1, 152-3, 150- (N-1)) and the second M × N / 2 channel wavelength division multiplexed light are N / 2. The multi-wavelength light receiving element for receiving the M-channel multi-wavelength light is configured to have N / 2 pairs (152-2,152-4,150-N). The first periodic wavelength multiplexing / demultiplexing element 130 is connected to the second periodic wavelength multiplexing / demultiplexing element 140 via the optical fiber transmission line 113. The present embodiment is an optical transmission / reception system using a single-core fiber having a different transmission / reception direction for each adjacent pair.

  Each of the multi-wavelength light sources (110-1 to 110-N) includes M light sources 112 and a wavelength multiplexing element that wavelength-multiplexes M channel lights from the M light sources and outputs M channel wavelength multiplexed light. 114. For example, the frequency interval of the M channel lights from the M light sources 112-11 to 112-M1 of the multi-wavelength light source 110-1 is ΔF. The same applies to the multi-wavelength light sources 110-2 to 110-N. N / 2 sets of M channel wavelength multiplexed light from the N sets of multi-wavelength light sources (110-1 to 110-N) are M × N / 2 channel wavelength multiplexed light in the first periodic wavelength multiplexing / demultiplexing device 130. Wavelength multiplexed. The remaining N / 2 sets of M channel wavelength multiplexed light from the N sets of multi-wavelength light sources (110-1 to 110-N) are M × N / 2 channel wavelengths in the second periodic wavelength multiplexing / demultiplexing device 130. Wavelength multiplexed into multiplexed light.

  Each of the multi-wavelength light receiving elements (150-1 to 150-N) receives a wavelength demultiplexing element 154 that wavelength-separates M channel wavelength multiplexed light and outputs M channel light, and M channel light. M light receiving elements 152 are provided. Each of the M light receiving elements 152 receives one of the M channel lights. For example, the wavelength demultiplexing element 154-1 of the multi-wavelength light receiving element 150-1 includes N sets of M channels demultiplexed from the M × N / 2-channel wavelength multiplexed light by the first periodic wavelength multiplexing / demultiplexing element 140. One of the wavelength multiplexed lights is demultiplexed into M channel lights, and these M channel lights are received by the M light receiving elements 152-11 to 152-M1, respectively. Similarly, the wavelength demultiplexing element 154-2 of the multi-wavelength light receiving element 150-2 includes N sets of M demultiplexed from the M × N / 2-channel wavelength multiplexed light by the second periodic wavelength multiplexing / demultiplexing element 140. One of the channel wavelength multiplexed lights is demultiplexed into M channel lights, and these M channel lights are respectively received by M light receiving elements.

  As the light source 112, a 1.3 μm band semiconductor laser is used, and the wavelength of the M × N channel is different. Each light source is integrated with an electroabsorption type modulation unit capable of performing a modulation operation with a data signal of 25 Gb / s.

Here, labels are assigned to wavelengths in N sets of multi-wavelength light sources. The wavelength of the first set of multi-wavelength light sources is M waves from λ ₁₁ to λ _M1 , and the wavelength of the second set of multi-wavelength light sources is M waves from λ ₁₂ to λ _M2 . Therefore, the M-th set of wavelengths is M waves from λ _1N to λ _MN .

  The operation of the optical transmission / reception system of FIG. 1 will be briefly described. The M-channel wavelength multiplexed signals output from the N sets of multi-wavelength light sources (110-1 to 110-N) are respectively the first periodic wavelength multiplexing / demultiplexing element 130 or the second periodic wavelength multiplexing / demultiplexing. Input to the input port of the element 140. The output is an M × N / 2 channel wavelength multiplexed signal and propagates in the optical fiber transmission line 113. After propagation, the first periodic wavelength multiplexing / demultiplexing element 130 or the second periodic wavelength multiplexing / demultiplexing element 140 demultiplexes into a wavelength group equivalent to each multi-wavelength light source (N sets of M-channel wavelength multiplexed signals). After that, each of the multi-wavelength light receiving elements (150-1 to 150-N) is re-demultiplexed into M channel lights by the wavelength demultiplexing element 154 and then received by the M light receiving elements 152.

  For example, when each multi-wavelength light source (110) has a wavelength multiplexing number of 4 channels and each light source 112 has a modulation speed of 25 Gb / s, the total bit rate of each multi-wavelength light source is 100 Gb / s. Furthermore, by using four sets of multi-wavelength light sources (110-1 to 110-N; N = 4), a total bit rate of 400 Gb / s can be obtained from the periodic wavelength multiplexing / demultiplexing element. In the present embodiment, since the optical transmission / reception system is a single-core fiber having a different transmission / reception direction for each adjacent pair, the total bit rate in each direction is 200 Gb / s.

FIG. 2 shows the wavelength arrangement in this example. The wavelength of the M × N channel is roughly divided into M groups of N channels. For example, the first group is composed of N waves from λ ₁₁ to λ _1N , and the subsequent second group is composed of N waves from λ ₂₂ to λ _2N . Here, the frequency interval between adjacent groups (for example, the interval between λ ₁₁ and λ ₂₁ ) is ΔF, the adjacent frequency interval within the same group (for example, the interval between λ ₂₁ and λ ₂₂ ) is Δf, and the transmission band (path) in each group (Band) is B.

  The present embodiment is configured to assume 200 Gb / s bidirectional transmission, which is 100 GbE extended. Considering the factors, the main parameters were set to the following numerical values.

M = 4
N = 4
ΔF = 800GHz
Δf = 100 GHz
B = 360GHz
Therefore, in this configuration, each group has four-wave WDM at 100 GHz intervals, and the frequency interval for each group is 800 GHz. That is, in the proposed optical transmission / reception system, M × N WDM optical wavelengths are not necessarily arranged at the same frequency interval.

  In this configuration, N sets of M-channel multi-wavelength light sources (110-1 to 110-N) have the frequency of adjacent sets shifted by Δf as a whole, and N sets of interval products Δf × (N− One feature is that 1) is smaller than the transmission band B of the wavelength demultiplexing element 154 in the multi-wavelength light receiving element 150.

  Next, a configuration example of the first periodic wavelength multiplexing / demultiplexing element 130 and the second periodic wavelength multiplexing / demultiplexing element 140 for realizing the above configuration will be described with reference to FIG. Here, the first periodic wavelength multiplexing / demultiplexing element 130 will be described as a configuration diagram, but the description as the second periodic wavelength multiplexing / demultiplexing element 140 can be similarly performed by making the traveling direction of light symmetrical. is there.

  The periodic wavelength multiplexing / demultiplexing device shown in FIG. 3 is a PLC type arrayed waveguide grating (AWG) manufactured in an optical planar circuit (PLC) 300. The periodic wavelength multiplexing / demultiplexing device includes an input / output channel waveguide (302-1 to 302-N), a wavelength division multiplexing waveguide (310), an input / output slab waveguide 304, a wavelength division multiplexing slab waveguide 308, and an array waveguide. 306. There are at least N input / output channel waveguides and at least one wavelength multiplexing waveguide.

  Here, as a circuit design condition, the period (free spectrum range, FSR) of the periodic wavelength multiplexing / demultiplexing element is configured to be equal to the frequency interval ΔF of the multi-wavelength light sources (110-1 to 110-N). Further, the interval (port interval) of the input / output channel waveguides (302-1 to 302-N) at the connection point with the input / output slab waveguide 304 is equal to Δf, and the input / output slab waveguide 304 and the arrayed waveguide 306 are provided. The input light propagated through the wavelength multiplexing slab waveguide 308 is configured to focus on the wavelength multiplexing waveguide 310 connected to the wavelength multiplexing slab waveguide.

Of the N input / output channel waveguides (302-1 to 302-N), the odd-numbered number, that is, the input / output channel waveguides 302-1 and 302-3 to 302- (N-1) have a multi-wavelength light source (110− 1 to 110-N), odd numbers, that is, wavelengths from the multi-wavelength light sources 110-1 and 110-3 to 110- (N-1) are input. Further, even numbers among the N input / output channel waveguides, that is, the input / output channel waveguides 302-2 and 302-4 to 302-N are even numbers among the multi-wavelength light receiving elements (150-1 to 150-N). That is, the wavelengths to the multi-wavelength light receiving elements 150-2 and 150-4 to 150-N are output. That is, M waves of wavelengths λ ₁₁ to λ _M1 of the first set of multi-wavelength light sources are input to the first input / output channel waveguide, and the second set of multi-wavelength light receiving is input to the second input / output channel waveguide. M waves of wavelengths λ ₁₂ to λ _M2 are output to the element. M waves of wavelengths λ ₁₃ to λ _{M (N−1)} of the third set of multi-wavelength light sources are input to the third input / output channel waveguide, and the Nth set ( M waves of wavelengths λ _1N to λ _MN are output to the multi-wavelength light receiving element of N = 4). By alternately connecting the multi-wavelength light source and the multi-wavelength light receiving element to odd numbers and even numbers among the N input / output channel waveguides, crosstalk between the four-wave WDMs can be reduced.

  Based on the above design conditions and input conditions, a set of M-channel wavelength multiplexed light input to N / 2 of N input / output channel waveguides (302-1 to 302-N) is a wavelength multiplexed waveguide 310. Are output as WDM signals of M × N / 2 channels.

  In this embodiment, since N = 4, there are four input / output channel waveguides. Since M = 4, 16 waves (4 × 4) of WDM signals are input / output from the wavelength multiplexing waveguide when the two directions are combined. Here, the port interval Δf of the periodic wavelength multiplexing / demultiplexing element may be such that the product Δf × (N−1) is equal to or less than half of the FSR periodicity (free spectral range, FSR) ΔF. As a result, an optical circuit (periodic wavelength multiplexing / demultiplexing device) having low loss characteristics can be realized.

  FIG. 4 shows a circuit configuration of the periodic wavelength multiplexing / demultiplexing device 300 used in this embodiment. As shown in FIG. 4, the first periodic wavelength multiplexing / demultiplexing element 130 and the second periodic wavelength multiplexing / demultiplexing element 140 are the same. As a result, the optical circuit (the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element) can be reduced in size and economy. The periodic wavelength multiplexing / demultiplexing element 300 includes N wavelength multiplexing input / output channel waveguides 302, wavelength multiplexing input / output slab waveguides 304, wavelength multiplexing array waveguides 306, and wavelength multiplexing wavelengths. The multi-slab waveguide 308 and one wavelength multiplexing wavelength multiplexing waveguide 310 are configured.

FIG. 5 shows a characteristic example of the manufactured 4 × 1 periodic wavelength multiplexing / demultiplexing element. This element is a silica-based PLC on a silicon substrate, and the relative refractive index difference between the core and the clad is about 1%. The obtained characteristics have a low loss of 1.5 dB or less from λ ₁₁ to λ ₄₄ . Further, the frequency interval between adjacent groups (for example, the interval between λ ₁₁ and λ ₂₁ ) ΔF and the adjacent frequency interval within the same group (for example, the interval between λ ₂₁ and λ ₂₂ ) Δf are 800 GHz and 100 GHz, respectively, as designed. Was less than the measurement accuracy (± 4 GHz). In addition, regarding the characteristic difference (polarization dependence) in the two polarization directions of light, in FIG. 5, both polarization directions were overlaid, but the polarization dependence could not be identified (measured by frequency difference). It can be seen that it has good characteristics (below accuracy).

  Next, set wavelengths of the multi-wavelength light source 110 will be described with reference to FIG. As described above, the frequency interval ΔF of the multi-wavelength light sources (110-1 to 110-N) is 800 GHz, the number of channels M is 4, and the set N is 4. The M × N channels all have different oscillation wavelengths (oscillation frequencies), and the frequencies of adjacent sets are shifted by Δf as a whole. In order to make such wavelengths uniform, there is a method of preparing light sources having different compositions shifted by Δf, but in this embodiment, a method of using light sources having the same composition is adopted. That is, this is a method of adjusting the oscillation wavelength by adjusting the temperature.

  The multi-wavelength light source used is one in which each light source (M light sources 112) is integrated on the same substrate. Therefore, it is possible to collectively change all wavelengths of the multi-wavelength light source by adjusting the temperature for each substrate by temperature control means such as a Peltier element or a heater. Since the wavelength variation due to temperature is about 15 GHz per 1 ° C., a temperature change of about 7 ° C. is sufficient to give Δf of 100 GHz.

In FIG. 6, the temperature of the same multi-wavelength light source is plotted on the horizontal axis and the oscillation wavelength is plotted on the vertical axis. According to this, four waves from λ ₁₁ to λ ₄₁ are obtained when the operating temperature is about 40 ° C., and the remaining wavelengths are obtained each time the temperature is increased, and from the longest wavelength λ ₁₄ at about 57 ° C. it is possible to generate a wavelength of lambda _44.

  Considering general laser performance, it is desirable to set the temperature control range within ± 20 ° C. That is, it is desirable that the frequency control range is within 600 GHz in total width.

  Therefore, in the M-channel multi-wavelength light source of the present embodiment, N sets of interval products Δf × (N−1) are set to 600 GHz or less. This makes it possible to use the same component. Therefore, the system can be further simplified and made economical.

  FIG. 7 shows an output spectrum waveform when it is input to the periodic wavelength multiplexing / demultiplexing element in which the multi-wavelength light source is manufactured. In this experiment, since the same multi-wavelength light source is used as four sets of multi-wavelength light sources (using the wavelength adjustment shown in FIG. 6), the output spectrum of FIG. 4 is an overlay of four output spectra obtained from a channel waveguide.

  As a result of the experiment, ΔF was 800 GHz, Δf was 100 GHz, and each lane could be allocated within the transmission band B (360 GHz) as shown in FIG.

  From the above results, according to the present embodiment, in the optical transmission / reception system as shown in FIG. 1, by setting the period of the periodic wavelength multiplexing / demultiplexing element to a condition equal to the frequency interval ΔF of the multi-wavelength light source, The WDM system can be expanded to a single-core bidirectional optical transmission / reception WDM with a simple configuration and higher density and higher bit rate.

  In this embodiment, the wavelength of the light source is set to the 1.3 μm band, but a 1.5 μm band which is a telecom wavelength may be used. The light source modulation unit is an electroabsorption type, but direct laser modulation may be used, or a modulator using an electro-optic crystal such as lithium niobate and a light source may be used in combination.

  Furthermore, in this configuration, since N sets of interval products Δf × (N−1) are smaller than the transmission band B of the wavelength demultiplexing element in the multiwavelength light receiving element, each multiwavelength light receiving element includes the same wavelength demultiplexing characteristics. It is possible to use these parts. Therefore, the system can be further simplified and made economical.

  In this embodiment, Δf is set to 100 GHz. However, if N waves in the same group are in the transmission band B, the above effect can be maintained even at other values, for example, 75 GHz and 50 GHz.

  In this embodiment, since the M channel multi-wavelength light sources have N sets of interval products Δf × (N−1) within 600 GHz, each multi-wavelength light source includes the same components including the oscillation wavelength characteristics of the light sources. Can be used. Therefore, the system can be further simplified and made economical.

  In this example, a PLC type arrayed waveguide diffraction grating (AWG) is applied to the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. As a result, an optical circuit that is smaller and simpler than the conventional interleave type filter can be realized.

  The PLC of the present embodiment is a quartz waveguide on a silicon substrate, but the material of the substrate and the waveguide is not limited to silicon or quartz, and an organic polymer resin or the like can also be used.

  Further, by adding a temperature compensation function, that is, an athermal function, to the PLC of this embodiment, an optical circuit whose characteristics do not change even when the environmental temperature changes can be obtained. As a typical addition of the athermal function, there is a method of inserting a material having a thermal expansion coefficient symmetrical to the thermal expansion coefficient of the optical waveguide between the waveguides.

  In this embodiment, the product Δf × (N−1) of the port interval Δf of the periodic wavelength multiplexing / demultiplexing element is set to half or less of the periodicity ΔF. As a result, as shown in the result of FIG. 5, the wavelength used can be near the center in the FSR, so that an optical circuit with low loss characteristics can be realized.

  Furthermore, as shown in FIG. 4, by making the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element the same, further downsizing of the optical circuit can be realized.

(Second Embodiment)
Next, with reference to FIG. 8, an optical transmission / reception system and an optical circuit thereof according to a second embodiment of the present invention will be described. Since the configuration of the optical transmission / reception system of this embodiment is the same as the configuration shown in FIGS. The difference from the first embodiment is the circuit configuration of the periodic wavelength multiplexing / demultiplexing element. FIG. 8 shows a configuration of a periodic wavelength multiplexing / demultiplexing element in this example. Here, the first periodic wavelength multiplexing / demultiplexing element 130 will be described as a configuration diagram. However, the second periodic wavelength multiplexing / demultiplexing element 140 can be similarly explained by making the traveling direction of light symmetrical. It is. The configuration of the second periodic wavelength multiplexing / demultiplexing element may be the same as that of the first periodic wavelength multiplexing / demultiplexing element described with reference to FIG. 3 (the light traveling direction is symmetric with respect to FIG. 3).

  The periodic wavelength multiplexing / demultiplexing device in FIG. 8 is a PLC type AWG fabricated in an optical planar circuit (PLC) 800 as in the first embodiment, and includes an input / output channel waveguide 302, a wavelength multiplexing waveguide 310, The input / output slab waveguide 304, the wavelength multiplexing slab waveguide 308, and the arrayed waveguide 306 are configured. There are at least N input / output channel waveguides and at least one wavelength multiplexing waveguide.

  Further, as one of the features of the present embodiment, the periodic wavelength multiplexing / demultiplexing element has an input / output channel waveguide 302 connected to the input / output slab waveguide 304, and detects and controls the wavelength of each multi-wavelength light source. A wavelength-division-multiplexed waveguide 310 is connected to the wavelength-division-multiplexed slab waveguide 308, and a part of the output wavelength-multiplexed light is re-input to the wavelength-division-multiplexed slab waveguide 308. Loopback waveguides 804 are connected.

  A tap circuit 806 is inserted in the output portion of the periodic wavelength multiplexing / demultiplexing element, and a part of the wavelength multiplexed light is connected to the loopback waveguide 804 via the connection waveguide 808. The tap circuit 806 is an optical component that can be configured with a directional coupler, a Y branch circuit, or the like. In this embodiment, 5% of the total intensity of wavelength multiplexed light is extracted and connected to the loopback waveguide 804.

  Basic circuit design conditions are the same as in the first embodiment. That is, the period of the periodic wavelength multiplexing / demultiplexing element is configured to be equal to the frequency interval ΔF of the multi-wavelength light source. Further, the interval (port interval) of the input / output channel waveguide 302 at the connection point with the input / output slab waveguide 304 is equal to Δf, and the input / output slab waveguide 304, the arrayed waveguide 306, and the wavelength multiplexing slab waveguide 308 are The propagated input light is configured to focus on the wavelength division multiplexing waveguide 310 connected to the wavelength division multiplexing slab waveguide 308.

Of the N input / output channel waveguides 302, odd-numbered numbers, that is, input / output channel waveguides 302-1, 302-3 to 302- (N-1) include multi-wavelength light sources (110-1 to 110-N). Of these, odd numbers, that is, wavelengths from the multi-wavelength light sources 110-1, 110-3 to 110- (N-1) are input. Further, even numbers among the N input / output channel waveguides, that is, the input / output channel waveguides 302-2 and 302-4 to 302-N are even numbers among the multi-wavelength light receiving elements (150-1 to 150-N). That is, the wavelengths to the multi-wavelength light receiving elements 150-2 and 150-4 to 150-N are output. That is, M waves of wavelengths λ ₁₁ to λ _M1 of the first set of multi-wavelength light sources are input to the first input / output channel waveguide, and the second set of multi-wavelength light receiving is input to the second input / output channel waveguide. M waves of wavelengths λ ₁₂ to λ _M2 are output to the element. M waves of wavelengths λ _{13 to} λ _{M (N−1)} of the third set of multi-wavelength light sources are input to the third input / output channel waveguide, and the Nth set ( M waves of wavelengths λ _1N to λ _MN are output to the multi-wavelength light receiving element of N = 4). The parameters in this embodiment are M = 4, N = 4, Δf = 100 GHz, and ΔF = 800 GHz.

  The design of the monitor waveguide 802 and the loopback waveguide 804, which is one of the characteristic structures of this embodiment, will be described.

  The number of monitor waveguides 802 is N for N sets of multi-wavelength light sources. Similar to the input / output channel waveguide 302, the interval (port interval) of the N monitor waveguides 802 at the connection point of the input / output slab waveguide 304 is set to Δf, and adjacent to the input / output channel waveguide 302 in order. Deploy. In this embodiment, the input / output channel waveguide 302 is symmetrically disposed at the center of the input / output slab waveguide in order to obtain low loss. Therefore, the monitor waveguide 802 is symmetrically disposed on both outer sides of the N input / output channel waveguides 302 as shown in FIG.

  The loopback waveguide 804 is arranged at a position that is Δf × N away from the connection point between the wavelength division multiplexing slab waveguide 308 and the wavelength division multiplexing waveguide 310.

  Based on the above design conditions and input conditions, as in the first embodiment, a set of M-channel wavelength multiplexed light that is input to N / 2 of the N input / output channel waveguides 302 is It is output as a WDM signal of M × N / 2 channels. In this embodiment, since N = 4, there are four input / output channel waveguides. Since M = 4, 16 waves (4 × 4) of WDM signals are output from the wavelength multiplexing waveguide when the two directions are combined.

  Furthermore, as a feature of the present embodiment, a part of the wavelength multiplexed light returned from the loopback waveguide 804 to the wavelength multiplexed slab waveguide 308 is wavelength-demultiplexed and then output to each monitor waveguide 802. The wavelength group output to each monitor waveguide has M channels at a frequency interval ΔF, which is equivalent to the wavelength group of each multi-wavelength light source. Therefore, it is possible to adjust (feedback control) the wavelength and light intensity of each multi-wavelength light source by monitoring the wavelength and light intensity from each monitor waveguide.

  The structure and function described above can be realized with almost no increase in the chip size of the AWG and almost no deterioration of the wavelength multiplexing / demultiplexing characteristics.

  As described above, according to the present embodiment, by using the periodic wavelength multiplexing / demultiplexing device as shown in FIG. 8, the existing WDM system can be easily configured with a higher density, higher bit rate, and a single core bidirectional type. Can be extended to optical transmission / reception WDM.

  In this embodiment, the input / output channel waveguide 302 is symmetrically disposed at the center of the input / output slab waveguide in order to obtain low loss, but may be located at another position as long as it is within the FSR. For example, each input / output channel waveguide can be connected to a position shifted by Δf × N. In that case, four monitor waveguides 802 are arranged adjacent to the four input / output channel waveguides under the design conditions of the present embodiment.

(Third embodiment)
Next, with reference to FIGS. 9 to 11, an optical transmission / reception system and an optical circuit thereof according to a third embodiment of the present invention will be described. Since the configuration of the optical transmission / reception system of this embodiment is the same as the configuration shown in FIGS. The difference from Embodiments 1 and 2 is the circuit configuration of the periodic wavelength multiplexing / demultiplexing element. FIG. 9 shows a configuration of a periodic wavelength multiplexing / demultiplexing element in this example. Here, the first periodic wavelength multiplexing / demultiplexing element 130 will be described as a configuration diagram. However, the second periodic wavelength multiplexing / demultiplexing element 140 can be similarly explained by making the traveling direction of light symmetrical. It is. The configuration of the second periodic wavelength multiplexing / demultiplexing element may be the same as that of the first periodic wavelength multiplexing / demultiplexing element described with reference to FIG. 3 (the light traveling direction is symmetric with respect to FIG. 3).

  The periodic wavelength multiplexing / demultiplexing device in FIG. 9 is a PLC type arrayed waveguide diffraction grating (AWG) manufactured in an optical planar circuit (PLC) 900 as in the above embodiment. The input / output channel waveguide 302 and the wavelength division multiplexing waveguide 310, the input / output slab waveguide 304, the wavelength division multiplexing slab waveguide 308, and the arrayed waveguide 306 are configured. There are at least N input / output channel waveguides 302 and at least one wavelength multiplexing waveguide 310.

  As in the second embodiment, the periodic wavelength multiplexing / demultiplexing device includes an input / output channel waveguide 302 connected to the input / output slab waveguide 304 and a monitor guide for detecting and controlling the wavelengths of the multi-wavelength light sources. A waveguide 802 is connected, and the wavelength multiplexing slab waveguide 308 is connected to the wavelength multiplexing slab waveguide 308, and a loop-back waveguide for re-inputting a part of the output wavelength multiplexed light to the wavelength multiplexing slab waveguide 308. A waveguide 904 is connected.

  Further, as one of the features of the present embodiment, the periodic wavelength multiplexing / demultiplexing element is connected to the wavelength division multiplexing slab waveguide 308 and the wavelength division multiplexing waveguide 310, and extracts a part of the wavelength division multiplexed light to be output. A tap circuit 906 is connected to the wavelength multiplexing waveguide 310, and one of the tap circuits is connected to the loopback waveguide 904. The tap circuit 906 is an optical circuit that can be configured with a directional coupler, a Y branch circuit, or the like. In this embodiment, 5% of the total intensity of wavelength multiplexed light is extracted and connected to the loopback waveguide 904.

  Basic circuit design conditions are the same as those in the first and second embodiments. That is, the period of the periodic wavelength multiplexing / demultiplexing element is configured to be equal to the frequency interval ΔF of the multi-wavelength light source. Further, the interval (port interval) of the input / output channel waveguide 302 at the connection point with the input / output slab waveguide 304 is equal to Δf, and propagates through the input / output slab waveguide 304, the arrayed waveguide 306, and the output slab waveguide 308. The input light is configured to focus on the wavelength division multiplexing waveguide 310 connected to the output slab waveguide 308.

Of the N input / output channel waveguides (302-1 to 302-N), an odd number, that is, the input / output channel waveguides 302-1 and 302-3 to 302- (N-1) have a multi-wavelength light source (for example, 110-1 to 110-N), an odd number, that is, a wavelength from 110-1, 110-3 to 110- (N-1) is input. Further, even numbers among the N input / output channel waveguides, that is, the input / output channel waveguides 302-2 and 302-4 to 302-N are even numbers among the multi-wavelength light receiving elements (150-1 to 150-N). That is, the wavelengths to the multi-wavelength light receiving elements 150-2 and 150-4 to 150-N are output. That is, M waves of wavelengths λ ₁₁ to λ _M1 of the first set of multi-wavelength light sources are input to the first input / output channel waveguide, and the second set of multi-wavelength light receiving is input to the second input / output channel waveguide. M waves of wavelengths λ ₁₂ to λ _M2 are output to the element. M waves of wavelengths λ _{13 to} λ _{M (N−1)} of the third set of multi-wavelength light sources are input to the third input / output channel waveguide, and the Nth set ( M waves of wavelengths λ _1N to λ _MN are output to the multi-wavelength light receiving element of N = 4). The parameters in this embodiment are M = 4, N = 4, Δf = 100 GHz, and ΔF = 800 GHz.

  The number of monitor waveguides 802 is N for N sets of multi-wavelength light sources. Similar to the input / output channel waveguide 302, the interval (port interval) of the N monitor waveguides 802 at the connection point of the input / output slab waveguide 304 is set to Δf, and adjacent to the input / output channel waveguide 302 in order. Deploy. In this embodiment, the input / output channel waveguide 302 is symmetrically disposed at the center of the input / output slab waveguide in order to obtain low loss. Therefore, the monitor waveguide 802 is symmetrically disposed on both outer sides of the N input / output channel waveguides 302 as shown in FIG.

  The loopback waveguide 904 is disposed at a position that is Δf × N away from the connection point between the output slab waveguide 308 and the wavelength division multiplexing waveguide 310.

  Based on the above design conditions and input conditions, as in the first embodiment, a set of M channel wavelength multiplexed light input to M / 2 of the N input / output channel waveguides 302 is transmitted in the wavelength multiplexed waveguide 310. It is output as a WDM signal of M × N / 2 channels. In this embodiment, since N = 4, there are four input / output channel waveguides. Since M = 4, 16 waves (4 × 4) of WDM signals are output from the wavelength multiplexing waveguide when the two directions are combined.

  A part of the wavelength multiplexed light returned from the loopback waveguide 904 to the output waveguide slab waveguide 308 is demultiplexed and then output to each monitor waveguide 802. The wavelength group output to each monitor waveguide has M channels at a frequency interval ΔF, which is equivalent to the wavelength group of each multi-wavelength light source. Therefore, it is possible to adjust (feedback control) the wavelength and light intensity of each multi-wavelength light source by monitoring the wavelength and light intensity from each monitor waveguide.

  The structure and function described above can be realized with almost no increase in the chip size of the AWG and almost no deterioration of the wavelength multiplexing / demultiplexing characteristics.

  Further, since the tap circuit 906 is integrated on the same chip in this embodiment, the degree of integration can be improved without deterioration in size and characteristics as compared with the second embodiment.

  FIG. 10 shows a circuit configuration of the periodic wavelength multiplexing / demultiplexing device 900 used in this embodiment. As shown in FIG. 10, the first periodic wavelength multiplexing / demultiplexing element 130 and the second periodic wavelength multiplexing / demultiplexing element 140 are the same. As a result, the optical circuit (the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element) can be reduced in size and economy. The periodic wavelength multiplexing / demultiplexing device 900 includes N wavelength multiplexing input / output channel waveguides 302, a wavelength multiplexing input / output slab waveguide 304, a wavelength multiplexing array waveguide 306, and a wavelength multiplexing wavelength. The multi-slab waveguide 308 and one wavelength multiplexing wavelength multiplexing waveguide 310 are configured.

  Similarly to the second embodiment, the periodic wavelength multiplexing / demultiplexing device 300 includes an input / output channel waveguide 302 connected to the input / output slab waveguide 304, and detects and controls the wavelengths of the multi-wavelength light sources. A loop for connecting the monitor waveguide 802 and the wavelength division multiplexing slab waveguide 308 to the wavelength division multiplexing waveguide 310 and re-inputting a part of the wavelength division multiplexed light to the wavelength division multiplexing slab waveguide 308 A back waveguide 904 is connected, and a tap circuit 906 for extracting a part of the wavelength multiplexed light output from the wavelength multiplexed waveguide 310 is connected to the wavelength multiplexed waveguide 310, and one of the tap circuits is a loop back waveguide. 904 is connected.

FIG. 11 shows the first set (M waves of wavelengths λ ₁₁ to λ _M1 of the first set of multi-wavelength light sources) among the characteristic examples of the fabricated 4 × 1 periodic wavelength multiplexing / demultiplexing element. This element is a silica-based PLC on a silicon substrate, and the relative refractive index difference between the core and the clad is about 1%. The obtained characteristics have a low loss of 1.5 dB or less from λ ₁₁ to λ ₄₄ . Further, the frequency interval between adjacent groups (for example, the interval between λ ₁₁ and λ ₂₁ ) ΔF and the adjacent frequency interval within the same group (for example, the interval between λ ₂₁ and λ ₂₂ ) Δf are 800 GHz and 100 GHz, respectively, as designed. Was less than the measurement accuracy (± 4 GHz). Furthermore, regarding the characteristic difference (polarization dependency) in the two polarization directions of light, FIG. 11 shows both polarization directions superimposed, but the polarization dependency cannot be identified (measured by frequency difference). (Less than accuracy). Also, monitor output light can be obtained at a position 20 dB lower than the wavelength-multiplexed output light. From this result, it is possible to adjust (feedback control) the wavelength and light intensity of each multi-wavelength light source by monitoring the wavelength and light intensity from each monitor waveguide.

  As described above, according to the present embodiment, by using the periodic wavelength multiplexing / demultiplexing device as shown in FIG. 9, the existing WDM system can be easily configured with a higher density, higher bit rate, and a single core bidirectional type. Can be extended to optical transmission / reception WDM.

  In the various embodiments described above, the example in which the multi-wavelength light source and the multi-wavelength light receiving element are alternately connected to the odd number and the even number of the N input / output channel waveguides has been described. The multi-wavelength light source and the multi-wavelength light receiving element need not be alternately connected to the waveguide. For example, a multi-wavelength light source may be connected from the first to N / 2 of the N input / output channel waveguides, and a multi-wavelength light receiving element may be connected to the rest.

DESCRIPTION OF SYMBOLS 100 Optical transmission / reception system 110 Multi-wavelength light source 111 Downstream signal light transmitter 112 Light source 113 Optical fiber transmission line 114 Wavelength multiplexing element 115 Signal light receiver 116 Upstream signal light transmitter 117 Upstream signal light receiver 130 1st periodic wavelength Multiplexing / demultiplexing element 140 Second periodic wavelength multiplexing / demultiplexing element 145 Periodic wavelength multiplexing / demultiplexing element 150 Multi-wavelength light receiving element 152 Light receiving element 154 Wavelength demultiplexing element 300, 800, 900 Optical planar circuit (PLC)
302 I / O channel waveguide 304 I / O slab waveguide 306 Array waveguide 308 Wavelength multiplexed slab waveguide 310 Wavelength multiplexed waveguide 802 Monitor waveguide 804, 904 Loopback waveguide 806, 906 Tap circuit 808 Connection waveguide

Claims (8)

N sets of M-channel multi-wavelength light sources having a frequency interval ΔF,
M-channel wavelength multiplexed light combined with the M channels, and N / 2 sets of M channel wavelength multiplexed light from each of the N / 2 sets of multi-wavelength light sources out of the N sets of multi-wavelength light sources, A first periodic wavelength-multiplexed light that is multiplexed with one M × N / 2-channel wavelength multiplexed light and a second M × N / 2-channel wavelength-multiplexed light is demultiplexed into N / 2 sets of M-channel wavelength multiplexed light. A demultiplexing element;
N / 2 sets of M-channel wavelength multiplexed light from each of the other N / 2 sets of multi-wavelength light sources among the N sets of multi-wavelength light sources are converted into the second M × N / 2-channel wavelength multiplexed light. A second periodic wavelength multiplexing / demultiplexing element that multiplexes and demultiplexes the first M × N / 2 channel wavelength multiplexed light into the N / 2 sets of M channel wavelength multiplexed light;
N / 2 sets of multi-wavelength light receiving elements for receiving N / 2 sets of M-channel multi-wavelength light demultiplexed by the first periodic wavelength multiplexing / demultiplexing elements and the second periodic wavelength multiplexing / demultiplexing elements And another N / 2 sets of multi-wavelength light receiving elements that receive the N / 2 sets of M-channel multiwavelength light demultiplexed by
The optical transmission / reception characterized in that the period of the first periodic wavelength multiplexing / demultiplexing element and the period of the second periodic wavelength multiplexing / demultiplexing element are equal to the frequency interval ΔF of the multi-wavelength light source. system. The M-channel multi-wavelength light source is:
The frequency of the adjacent set is shifted by Δf as a whole,
2. The optical transmission / reception system according to claim 1, wherein N sets of interval products Δf × (N−1) are smaller than a transmission band B of a wavelength demultiplexing element in the multi-wavelength light receiving element. The M-channel multi-wavelength light source is:
The optical transmission / reception system according to claim 1, wherein N sets of interval products Δf × (N−1) are within 600 GHz. The optical transmission / reception system according to any one of claims 1 to 3, wherein the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are arrayed waveguide gratings. The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element have a port interval of Δf,
The port interval product Δf × (N−1) is equal to or less than half of the periodicity ΔF of the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element. The optical transmission / reception system according to claim 4. The optical transmission / reception system according to claim 4, wherein the first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are the same. The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are:
N input / output channel waveguides for inputting and outputting the M channel wavelength division multiplexed light;
An input / output slab waveguide connected to the N input / output channel waveguides;
A monitor waveguide connected to the input / output slab waveguide together with the N input / output channel waveguides for detecting and controlling the wavelength of the M-channel wavelength multiplexed light;
A wavelength multiplexed slab waveguide connected by the input / output slab waveguide and an arrayed waveguide;
A wavelength division multiplexing waveguide connected to the wavelength division multiplexing slab waveguide;
A loopback waveguide connected to the wavelength division slab waveguide together with the wavelength division waveguide for re-inputting a part of the output M × N / 2 channel wavelength division multiplexed light to the wavelength division slab waveguide. The optical transmission / reception system according to claim 4, further comprising: The first periodic wavelength multiplexing / demultiplexing element and the second periodic wavelength multiplexing / demultiplexing element are:
The wavelength division multiplexing waveguide is connected,
A tap circuit for extracting a part of the M × N / 2-channel wavelength multiplexed light;
The optical transmission / reception system according to claim 7, wherein a part of the extracted M × N / 2-channel wavelength division multiplexed light is connected to the loopback waveguide.

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