JP2011199759A - Device, transmission system, method, and transmission method for multiplexing optical signal division - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce reception of an unnecessary or illegal channel by a reception-side device, and to restrain facility cost and circuit scale in a transmission-side device.SOLUTION: An optical signal division multiplexing device 10 includes: a modulation part 12 for outputting modulation optical pulse signals S1A, S1B, S1C; a selection part 13 for generating and outputting a plurality of bundles S1CA, S1AB, S1BC of optical signals including one or more modulation optical pulse signals selected from among the modulation optical pulse signals; and a plurality of broadband optical encoders 14a, 14b, 14c respectively corresponding to the plurality of bundles of optical signals. Each of the broadband optical encoders encodes one or more modulation optical pulse signals included in a corresponding bundle of optical signals out of the plurality of bundles of optical signals to output one or more encoded chip pulse trains S2CA, S2AB, S2BC, and further includes a multiplexing part 15 for multiplexing the one or more encoded chip pulse trains output from each of the broadband optical encoders.

Description

  The present invention relates to an optical signal division multiplexing apparatus, an optical signal division multiplexing transmission system, an optical signal division multiplexing method, and an optical signal division multiplexing in which an optical code division multiplexing (OCDM) method and an optical wavelength division multiplexing (optical WDM) method are combined. It relates to a transmission method.

  In recent years, an optical multiplexing system that transmits optical pulse signals of a plurality of channels to one optical fiber has become widespread. As an optical multiplexing system, an optical time division multiplexing (OTDM) system, an optical WDM system, and an OCDM system are known. These methods are described in, for example, Non-Patent Document 1 (written by Hideyuki Tonobayashi). Also, an optical transmission system employing the optical WDM system is disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-165213). Furthermore, in the OCDM system, a superstructure fiber Bragg grating (SSFBG) is used for an optical encoder (optical decoder) that converts an optical pulse signal into an optical pulse signal encoded by a phase shift keying (PSK) system. Are disclosed in, for example, Non-Patent Document 2 (written by Akihiko Nishiki et al.) And Patent Document 2 (Japanese Patent Laid-Open No. 2008-153921).

  In the OCDM system, since the fiber Bragg grating (FBG) encoder performs optical signal encoding and wavelength identification, even if the code pattern of the generated optical pulse signal is the same, the FBG code handles different wavelengths. If a device is prepared, a new channel can be added. An optical multiplexing method combining the OCDM method and the optical WDM method has been studied for the purpose of increasing the number of channels by utilizing such characteristics of the FBG encoder. Such a system is disclosed, for example, in Non-Patent Document 3 (written by Taro Hamanaka et al.). Another optical multiplexing method combining the OCDM method and the optical WDM method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-257658.

Hideyuki Tonobayashi, “Optical Code Division Multiplexing Network”, Applied Physics, Vol. 71, No. 7, 2002, pp. 853-859 Nishiki Yasuhiko et al., "Development of phase encoder for OCDM using SSFBG", IEICE Tech., Technical Report of IEICE, OFT 2002-66, November 2002, pp. 13-18 Taro Hamanaka et al., “Demonstration of 16-user OCDMA over 3-wavelength WDM using 511-chip, 640 Gchip / s SSFBGen / decoder and single light Source.1”. 3, OFC2007

JP 2002-165213 A (paragraph 0009, FIG. 1) JP 2008-153922 A JP 2001-257658 A (paragraphs 0163-0169, FIG. 18, FIG. 19)

  However, any one of the above optical multiplexing systems was used to distribute data from a video distribution company's local equipment (transmission side apparatus) to a plurality of user side apparatuses (reception side apparatuses) through an optical communication line. In this case, the user side device also receives unnecessary channel data distributed to other users (see, for example, FIG. 1 of Patent Document 1). For this reason, when one optical multiplexing method is used, there is a problem that the user side device is likely to receive an unnecessary channel by mistake or receive an uncontracted channel illegally. .

  Further, in order to increase the number of channels that can be used for data distribution, when using an optical multiplexing method that combines an OCDM method and an optical WDM method, for example, one FBG encoder (transmission side device) is provided for each wavelength channel. ) And one FBG decoder (reception side device) must be prepared (see, for example, FIG. 3 of Non-Patent Document 3 and FIG. 18 of Patent Document 3). For this reason, in such a case, there is a problem that the cost per channel increases, and the mounting area of a circuit including a number of FBG encoders equal to the number of channels increases.

  Accordingly, the present invention has been made to solve the above-described problems, and can reduce reception of unnecessary or unauthorized channels by the receiving side apparatus, and suppress the equipment cost and circuit scale in the transmitting side apparatus. An object of the present invention is to provide an optical signal division multiplexing apparatus, an optical signal division multiplexing transmission system, an optical signal division multiplexing method, and an optical signal division multiplexing transmission method.

  An optical signal division multiplexing device according to an aspect of the present invention includes a modulated optical pulse output unit that outputs a plurality of modulated optical pulse signals having different wavelengths, and a wavelength selected from the plurality of modulated optical pulse signals. A plurality of broadband optical encoders each corresponding to each of the plurality of optical signal bundles; and a selection unit that generates and outputs a plurality of optical signal bundles including one or more modulated optical pulse signals. Each of the optical encoders encodes one or more modulated optical pulse signals included in a corresponding optical signal bundle among the plurality of optical signal bundles, and outputs one or more encoded chip pulse trains. And a multiplexing unit that multiplexes the one or more encoded chip pulse trains output from each of the plurality of wideband optical encoders.

  An optical signal division multiplex transmission system according to another aspect of the present invention includes a transmission-side apparatus that outputs a multiplexed optical signal to a transmission line, and a plurality of receptions that receive the multiplexed optical signal through the transmission line. An optical signal division multiplex transmission system comprising a side device, wherein the transmission side device is the optical signal division multiplex device, and the plurality of reception side devices correspond to any of the plurality of wideband optical encoders Each of the plurality of receiving side devices includes a narrowband variable optical decoder having a decodable band narrower than a codeable band of the corresponding wideband optical encoder, and the narrowband variable optical decoder Means for receiving the encoded one or more encoded chip pulse trains, selecting a wavelength of the optical signal to be decoded, and decoding the encoded pulse signal of the selected wavelength of the one or more encoded pulse signals Have It is characterized in.

  According to the present invention, it is possible to reduce the reception of unnecessary or unauthorized channels by the receiving side apparatus, and to suppress the equipment cost and the circuit scale in the transmitting side apparatus.

(A)-(e) is a figure which shows the operation | movement principle of the optical encoder and optical decoder using SSFBG. 1 is a diagram schematically showing a configuration of an optical signal division multiplexing device (transmission side device) and an optical signal division multiplexing transmission system including the same according to an embodiment of the present invention. FIG. It is a figure which shows the reflection spectrum which shows an example of the characteristic of the wideband optical encoder shown by FIG. (A)-(c) is a figure which shows the structure of the broadband optical encoder shown by FIG. 2, a periodic refractive index modulation structure part, and the length of the waveguide direction of each part. (A)-(c) is a figure which shows the reflection spectrum which shows an example of the characteristic of the narrow-band variable optical decoder shown by FIG. (A)-(c) is a figure which shows the encoding waveform of the wideband optical encoder shown by FIG. (A)-(c) is a figure which shows a decoding waveform (autocorrelation waveform) when the chip pulse train of a setting wavelength is input into the narrow-band variable optical decoder. (A) And (b) is a figure which shows an output waveform (cross correlation waveform) when the chip pulse train of wavelengths other than a setting wavelength is input into the narrow-band variable optical decoder. (A) And (b) is a figure which shows an output waveform (cross correlation waveform) when the chip pulse train of wavelengths other than a setting wavelength is input into the narrow-band variable optical decoder. (A) And (b) is a figure which shows an output waveform (cross correlation waveform) when the chip pulse train of wavelengths other than a setting wavelength is input into the narrow-band variable optical decoder.

  An optical signal division multiplexing apparatus combining an optical code division multiplexing (OCDM) system and an optical wavelength division multiplexing (optical WDM) system according to an embodiment of the present invention, and an optical signal including the optical signal division multiplexing apparatus are described below. An optical signal division multiplexing method that can be executed by a division multiplexing transmission system, an optical signal division multiplexing apparatus, and an optical signal division multiplexing transmission method that can be executed by an optical signal division multiplexing transmission system will be described.

<< 1 >> Description of Principle of OCDM System First, the principle of the OCDM system used in the present embodiment will be described. In the OCDM system, the optical encoder of the transmitting apparatus encodes an optical pulse signal with a different optical code for each communication channel to generate an encoded chip pulse train (encoded optical pulse train). The optical decoder of the reception side apparatus decodes the received encoded chip pulse train using the same optical code as that of the transmission side apparatus, and generates (restores) the original optical pulse signal.

  FIGS. 1A to 1E are diagrams illustrating the operation principle of the optical encoder 100 and the optical decoder 200 using SSFBG. 1A shows the waveform of the input optical pulse 300 input to the optical encoder 100, and FIG. 1B shows the waveform of the encoded chip pulse train output from the optical encoder 100. 1C shows the waveform of the component of the encoded chip pulse train output from the optical decoder 200, and FIG. 1D shows the autocorrelation waveform of the encoded chip pulse train output from the optical decoder 200. Show. FIG. 1 (e) shows a configuration for encoding and decoding the input optical pulse 300. In FIGS. 1C and 1D, # 1 to # 7 indicate the time relationship, and the smaller the value, the earlier the time.

  As shown in FIG. 1E, the optical encoder 100 is an SSFBG having four units FBGs 101, 102, 103, and 104 arranged along the waveguide direction of the optical fiber, and the code length is 4 bits. Have optical code values (for example, 0, 0, 1, 0). The optical decoder 200 is an SSFBG having four units FBGs 204, 203, 202, and 201 arranged along the waveguide direction of the optical fiber. The code length corresponding to the optical encoder 100 is a code value (4 bits). For example, 0, 1, 0, 0). The phase difference between the Bragg reflected light from the unit FBG with the code value 0 and the Bragg reflected light from the unit FBG with the code value 1 is π. Therefore, the code generated by the optical encoder 100 using the unit FBG is also referred to as an optical phase code.

  When the optical pulse 300 shown in FIG. 1 (a) is input to the optical encoder 100 via the optical fiber 111, the optical circulator 112, and the optical fiber 113, as shown in FIG. 1 (b), the unit FBG 101, An encoded chip pulse train 400 (chip pulses 401, 402, 403, 404) by Bragg reflected light a, b, c, d from 102, 103, 104 is generated. The phases of the Bragg reflected lights a, b, c, and d are 0, 0, π, and 0, respectively. In FIGS. 1B to 1D, the waveform of phase 0 is indicated by a solid line, and the waveform of phase π is indicated by a broken line. In FIG. 1 (e), the reflection that does not give a phase shift is indicated by a solid line arrow, and the reflection that gives a phase shift is indicated by a broken line arrow.

  The encoded chip pulse train 400 (chip pulses 401, 402, 403, 404) generated by the optical encoder 100 is optically decoded through the optical fiber 113, the optical circulator 112, the optical fiber 114, the optical circulator 211, and the optical fiber 212. Is input to the device 200. The optical decoder 200 has the same structure as that of the optical encoder 100, but the arrangement of the unit FBGs is reversed. That is, the unit FBGs 201, 202, 203, and 204 of the optical decoder 200 correspond to the units FBGs 101, 102, 103, and 104 of the optical encoder 100, respectively.

  When the chip pulse 401 (phase 0) shown in FIG. 1B is input to the optical decoder 200, as indicated by the reference numeral 501 in FIG. 1C, the unit pulses from the units FBGs 204, 203, 202, and 201 are displayed. An encoded chip pulse train 501 is generated by the Bragg reflected light a ′, b ′, c ′, d ′. The phases of the Bragg reflected light a ′, b ′, c ′, d ′ indicated by the encoded chip pulse train 501 correspond to 0, π, 0, 0 (time # 1, # 2, # 3, # 4, respectively). ).

  When the chip pulse 402 (phase 0) shown in FIG. 1 (b) is input to the optical decoder 200, as indicated by the reference numeral 502 in FIG. 1 (c), the unit pulses from the units FBGs 204, 203, 202, 201 are obtained. An encoded chip pulse train 502 is generated by the Bragg reflected light a ′, b ′, c ′, d ′. The phases of the Bragg reflected light a ′, b ′, c ′, d ′ indicated by the encoded chip pulse train 502 correspond to 0, π, 0, 0 (time # 2, # 3, # 4, # 5, respectively). ).

  When the chip pulse 403 (phase π) shown in FIG. 1B is input to the optical decoder 200, as indicated by reference numeral 503 in FIG. 1C, the unit pulses from the units FBGs 204, 203, 202, and 201 are displayed. An encoded chip pulse train 503 is generated by the Bragg reflected light a ′, b ′, c ′, d ′. The phases of the Bragg reflected lights a ′, b ′, c ′, d ′ indicated by the encoded chip pulse train 503 correspond to π, 0, π, π (time # 3, # 4, # 5, # 6, respectively). ).

  When the chip pulse 404 (phase 0) shown in FIG. 1 (b) is input to the optical decoder 200, as indicated by reference numeral 504 in FIG. 1 (c), from the units FBGs 204, 203, 202, 201. An encoded chip pulse train 504 is generated by the Bragg reflected light a ′, b ′, c ′, d ′. The phases of the Bragg reflected light a ′, b ′, c ′, d ′ indicated by the encoded chip pulse train 504 correspond to 0, π, 0, 0 (time # 4, # 5, # 6, # 7, respectively). ).

  All the chip pulses constituting the chip pulse train 500 shown in FIG. 1C are superimposed (added) to generate a white self-correlation waveform shown in FIG. In FIG. 1D, the maximum peak waveform at time # 4 is a waveform formed by superposing four chip pulses of the same phase (phase 0) at time # 4 shown in FIG. This is a waveform corresponding to the optical pulse 300.

  In the above description, the case where the code value of the optical code is 0, 0, 1, 0 is exemplified, but the same applies to other optical codes. In the above description, the case where the code length is 4 bits has been described, and the same applies to the case of a code length other than 4 bits.

  In optical code division multiplexing communication, multiplexing is performed by assigning different codes to each channel. In order to increase the number of multiplexed channels, at least the same number of different codes as the number of channels is required. In order to increase the number of different codes, the code length must be increased. For example, when using an M-sequence code having a code length of 15 bits, two codes can be used as different codes. In this case, 2-channel optical code division multiplexing communication can be realized. In order to realize optical code division multiplexing communication of more channels, it is necessary to use a code having a longer code length. For example, if the code length is increased to 31 bits, 33 types of codes can be prepared by combining M-sequence and Gold-sequence codes, and 33-channel optical code division multiplexing communication can be realized.

<< 2 >> Configuration of Embodiment FIG. 2 is a diagram schematically showing a configuration of an optical signal division multiplexing apparatus (transmission side apparatus) 10 and an optical signal division multiplexing transmission system including the same according to an embodiment of the present invention. is there. The optical signal division multiplexing apparatus 10 of the present embodiment is an apparatus that can implement the optical signal division multiplexing method of the embodiment according to the present invention, and the optical signal division multiplexing transmission system of the present embodiment is the present invention. 1 is a system capable of implementing an optical signal division multiplex transmission method according to an embodiment of the present invention. In this embodiment, both channel identification based on wavelength division multiplexing (WDM) and user side apparatus (reception side apparatus) identification based on optical code division multiplexing (OCDM) are used.

  As shown in FIG. 2, the optical signal division multiplexing transmission system according to the present embodiment includes an optical signal division multiplexing apparatus (transmission side apparatus) 10 in a local company side equipment and a plurality of user side apparatuses (reception side apparatuses). ) 30, 40, 50, a transmission line (optical communication line) 21 such as an optical cable, and a splitter 22. FIG. 2 shows an example in which data is distributed from the optical signal division multiplexing apparatus 10 to three user-side apparatuses 30, 40, and 50. Here, a case will be described in which data is distributed as an optical signal from one optical signal division multiplexing apparatus 10 to three user-side apparatuses 30, 40, 50. However, the number of user-side apparatuses (the number of user-side apparatuses) The number is not limited to three (three).

  The optical signal division multiplexing apparatus 10 includes a pulse signal generation unit 11, an optical modulation unit (modulated optical pulse output unit) 12, a selection unit 13, a plurality of broadband optical encoders 14a, 14b, and 14c, and a multiplexing unit. And a coupler 15 to be configured. Here, a case where the number of wideband optical encoders is three will be described, but this number is not limited to three.

  The user side device 30 includes a narrowband variable optical decoder 31 and an optical receiver 32 that receives the output of the narrowband variable optical decoder 31. The user side device 40 includes a narrowband variable optical decoder 41 and an optical receiver 42 that receives the output of the narrowband variable optical decoder 41. Further, the user side device 50 includes a narrowband variable optical decoder 51 and an optical receiver 52 that receives the output of the narrowband variable optical decoder 51.

  In the optical signal division multiplexer 10, the pulse signal generator 11 has a plurality of pulse generators 11a, 11b, and 11c. Each of the pulse generators 11a, 11b, and 11c generates pulse signals S0A, S0B, and S0C having different wavelengths WA, WB, and WC. Here, a case where the number of pulse generators is three will be described, but this number is not limited to three.

  The light modulation unit 12 includes a plurality of light modulators 12a, 12b, and 12c. Each of the optical modulators 12a, 12b, and 12c generates optical pulse signals S1A, S1B, and S1C having different wavelengths WA, WB, and WC. The optical modulators 12a, 12b, and 12c are devices that generate optical pulse signals S1A, S1B, and S1C based on input pulse signals S0A, S0B, and S0C, for example, laser light generators. The pulse generators 11a, 11b, and 11c are laser light generators that output optical pulses, and the optical modulators 12a, 12b, and 12c modulate the input optical pulse signals S0A, S0B, and S0C to generate optical pulse signals. The configuration may be S1A, S1B, or S1C.

  The selection unit 13 includes a plurality of splitters 13a, 13b, and 13c. The splitter 13a branches the optical pulse signal S1A output from the optical modulator 12a and supplies the same optical pulse signal S1A to the broadband optical encoder 14a and the broadband optical encoder 14b. The splitter 13b branches the optical pulse signal S1B output from the optical modulator 12b and supplies the same optical pulse signal S1B to the broadband optical encoder 14b and the broadband optical encoder 14c. The splitter 13c branches the optical pulse signal S1C output from the optical modulator 12c, and supplies the same optical pulse signal S1C to the broadband optical encoder 14c and the broadband optical encoder 14a. Thus, the selection unit 13 is a bundle of optical signals or an optical signal group (for example, an optical signal group) including one or more modulated optical pulse signals having a wavelength selected from the plurality of modulated optical pulse signals S1A, S1B, and S1C. A plurality of signals S1C and S1A (S1CA), optical signals S1A and S1B (S1AB), and optical signals S1B and S1C (S1BC) are generated and output. FIG. 3 shows a case where the selection unit 13 generates three optical signal bundles S1CA, S1AB, and S1BC.

  The selection unit 13 divides the three modulated optical pulse signals S1A, S1B, and S1C by splitters 13a, 13b, and 13c, and a wideband optical encoder 14a having three codes assigned to each user side device 30, 40, and 50. , 14b and 14c are physically selected and coupled. Only the signal of the wavelength channel required by each user side device 30, 40, 50 is input to the broadband optical encoders 14a, 14b, 14c corresponding to each user side device 30, 40, 50 by the selection unit 13. The Here, as an example, for the user side device 30, there is a usage contract for the channel Ch-C of the wavelength WC and the channel Ch-A of the wavelength WA, and for the user side device 40, the channel Ch-A of the wavelength WA. A case is described in which there is a usage contract for the channel Ch-B of the wavelength WB and the user side device 50 has a usage contract for the channel Ch-B of the wavelength WB and the channel Ch-C of the wavelength WC.

  The user side device 30 uses the wavelength setting unit 33 to select reception of either the channel Ch-C of the wavelength WC or the channel Ch-A of the wavelength WA. When the channel Ch-C of the wavelength WC is selected, the input encoded chip pulse train is input to the narrowband optical decoder 31C for the wavelength WC in the narrowband variable optical decoder 31, and the channel of the wavelength WA When Ch-A is selected, the input encoded chip pulse train is input to the narrowband optical decoder 31A for the wavelength WA in the narrowband variable optical decoder 31. The narrowband optical decoder 31C and the narrowband optical decoder 31A have the same code value. When the narrowband variable optical decoder 31 is for one wavelength channel, the wavelength setting unit 33 does not need to be provided.

  The user side device 40 uses the wavelength setting unit 43 to select reception of either the channel Ch-A of the wavelength WA or the channel Ch-B of the wavelength WB. When the channel Ch-A of the wavelength WA is selected, the input encoded chip pulse train is input to the narrowband optical decoder 41A for the wavelength WA in the narrowband variable optical decoder 41, and the channel of the wavelength WB When Ch-B is selected, the input encoded chip pulse train is input to the narrowband optical decoder 41B for the wavelength WB in the narrowband variable optical decoder 41. The narrowband optical decoder 41A and the narrowband optical decoder 41B have the same code value. When the narrowband variable optical decoder 41 is for one wavelength channel, the wavelength setting unit 43 need not be provided.

  The user side device 50 uses the wavelength setting unit 53 to select reception of either the channel Ch-B of the wavelength WB or the channel Ch-C of the wavelength WC. When the channel Ch-B of the wavelength WB is selected, the input coded chip pulse train is input to the narrowband optical decoder 51B for the wavelength WB in the narrowband variable optical decoder 51, and the channel of the wavelength WC When Ch-C is selected, the input encoded chip pulse train is input to the narrowband optical decoder 51C for the wavelength WC in the narrowband variable optical decoder 51. The narrowband optical decoder 51B and the narrowband optical decoder 51C have the same code value. When the narrow band variable optical decoder 51 is for one wavelength channel, the wavelength setting unit 53 does not need to be provided.

  The content of the usage contract by each user side device 30, 40, 50 is not limited to the above example. The number of contract channels is not limited to the above example, and may be other numbers as long as the number is 1 or more and the number of available channels or less.

  The plurality of broadband optical encoders 14a, 14b, and 14c correspond to the user side devices 30, 40, and 50, respectively. The chip pulse train generated by the encoding of the broadband optical encoder 14 a can be decoded by the user side device 30, and the chip pulse sequence generated by the encoding of the broadband optical encoders 14 b and 14 c is decoded by the user side device 30. Can not. Similarly, the chip pulse train generated by the encoding of the broadband optical encoder 14b can be decoded by the user side device 40, and the chip pulse train generated by the encoding of the broadband optical encoders 14a and 14c can be decoded by the user side device. Cannot decrypt with 40. Similarly, the chip pulse train generated by the encoding of the broadband optical encoder 14c can be decoded by the user side device 50, and the chip pulse train generated by the encoding of the broadband optical encoders 14b and 14c can be decoded by the user side device. Cannot decrypt with 50.

  The plurality of broadband optical encoders 14a, 14b, and 14c respectively correspond to a plurality of optical signal bundles S1CA, S1AB, and S1BC. The broadband optical encoder 14a can generate an encoded chip pulse train from each of optical pulses having three different wavelengths WA, WB, and WC. Similarly, the broadband optical encoder 14b can generate an encoded chip pulse train from each of optical pulses having three different wavelengths WA, WB, and WC. Similarly, the broadband optical encoder 14c can generate an encoded chip pulse train from each of optical pulses having three different wavelengths WA, WB, and WC. The broadband optical encoder 14a corresponding to the optical signal bundle S1CA encodes one or more modulated optical pulse signals included in the optical signal bundle S1CA (for example, the optical signal S1C or S1A included in the optical signal bundle S1CA). To output an encoded chip pulse train S2CA. Similarly, the broadband optical encoder 14b corresponding to the optical signal bundle S1AB includes one or more modulated optical pulse signals included in the optical signal bundle S1AB (for example, the optical signal S1A or S1B included in the optical signal bundle S1AB). ) And an encoded chip pulse train S2AB is output. Similarly, the broadband optical encoder 14c corresponding to the optical signal bundle S1BC includes one or more modulated optical pulse signals included in the optical signal bundle S1BC (for example, the optical signal S1B or S1C included in the optical signal bundle S1BC). ) And an encoded chip pulse train S2BC is output.

  The encoded chip pulse trains S2CA, S2AB, and S2BC are coupled (multiplexed) by the coupler 15, transmitted through the optical fiber 21, and distributed to each user side device 30, 40, 50 by the splitter 22. At this time, by setting the wavelengths of the unique narrowband variable optical decoders 31, 41, 51 possessed by each of the user side devices 30, 40, 50, the codes and wavelengths of the received encoded chip pulse train are matched. Narrowband variable optical decoders 31, 41, 51 having a code and a wavelength (wavelength set by the wavelength setting unit) perform decoding only from a coded chip pulse train having a matching code and wavelength, and decode (reproduce) The optical pulse signal thus supplied is supplied to the optical receivers 32, 42 and 52.

FIG. 3 is a diagram showing a reflection spectrum showing an example of characteristics of the broadband optical encoders 14a, 14b, and 14c shown in FIG. In FIG. 3, the codes of the broadband optical encoders 14a, 14b, and 14c are code lengths 31 and binary phase codes (0πππ000πππ0ππ000000ππππ0π0ππ000).
The case is shown. From FIG. 3, the broadband optical encoders 14a, 14b, and 14c have the highest reflectance at the center wavelength WB (for example, 1547.72 nm), and the reflectance decreases as the wavelength advances from the center wavelength WB to the short wavelength side. The reflectance decreases as the wavelength WB increases from the long wavelength side. However, the spectrum shape of the pattern similar to the wavelength WB is repeated in both the wavelength (for example, the wavelength WA) that proceeds from the central wavelength WB to the short wavelength side and the wavelength (for example, the wavelength WC) that proceeds to the long wavelength side. . In the present embodiment, the wavelengths of the optical signals of the three channels are set to wavelengths WA (15447.40 nm) and WC (1548.04 nm) of the spectral indentation indicated by arrows having a pattern similar to the center wavelength WB. ing.

4A to 4C show the structures of the broadband optical encoders 14a, 14b, and 14c shown in FIG. 2, the unit diffraction grating (unit FBG) that is a periodic refractive index modulation structure, and the waveguides of the respective parts. It is a figure which shows the length of a direction. As shown in FIGS. 4A to 4C, each of the plurality of broadband optical encoders 14a, 14b, and 14c is formed in the core (optical waveguide) 63 of the optical fiber 61 and the core 63. Chip pulses constituting a coded chip pulse train provided between a plurality of unit FBGs, which are a plurality of periodic refractive index distribution structure portions 62 arranged in the 63 waveguide direction (longitudinal direction of the optical fiber 61), and a plurality of unit FBGs. And a phase shift unit 64 that shifts one of the phases. The unit FBG is the Bragg reflection equation λ = 2n _eff × Λ ₀
A refractive index modulation period lambda ₀ of the diffraction grating according to, in the present embodiment, lambda is set to about 534.8Nm. N _eff is the effective refractive index of the core of the optical fiber.

  The reflection band can be controlled by controlling the unit diffraction grating length Lg with respect to the unit segment length Ls. In the present embodiment, since the broadband optical encoder structure unit is configured to handle three wavelengths (Nw = 3), it requires three times the band. Therefore, the unit segment length Ls is about 2.4 mm, and the unit diffraction grating length Lg is 1/3 (Ls / Nw) or less of the unit segment length Ls, and is about 0.8 mm here.

Thus, in each of the plurality of broadband optical encoders 14a, 14b, 14c,
A plurality of unit segments, which are sections divided into lengths equal to the waveguide direction, are determined in the core 63, and one of the plurality of unit FBGs is disposed in each of the plurality of unit segments. The unit diffraction grating length (unit FBG length) is Lg, the length of one unit segment in the waveguide direction is Ls, and each of a plurality of broadband optical encoders encodes modulated optical pulse signals of different frequencies. When the number is Nw,
Lg ≦ Ls / Nw
It is necessary to satisfy.

Further, the phase shift unit 64 is provided between the unit diffraction gratings of the phase shift amount according to the sign, and the shift amount between the unit diffraction gratings is a unit adjacent to the refractive index modulation period Λ ₀ . When the phase code of the diffraction grating is the same as [0, 0] or [π, π], the adjacent unit diffraction grating has a phase difference of 0 in the refractive index modulation, and the phase code of the adjacent unit diffraction grating is [0. , Π] or [π, 0], the refractive index modulation has a phase difference of 0.5 * Λ ₀ .

  The coupler 15 multiplexes the encoded chip pulse trains S2CA, S2AB, and S2BC output from each of the plurality of broadband optical encoders, and outputs the multiplexed signal to the transmission line 21 such as an optical cable. The multiplexed encoded chip pulse trains S2CA, S2AB, S2BC are branched by the splitter 22, and the encoded chip pulse sequences S2CA, S2AB, S2BC are input to the user side devices 30, 40, 50.

FIGS. 5A to 5C are diagrams showing reflection spectra showing examples of characteristics of the narrowband variable optical decoders 31, 41 and 51. 5A to 5C, the code of the narrowband variable optical decoder has the same code length 31 as that of the wideband optical encoder and a binary phase code (0πππ000πππ0ππ000000ππππ0π0ππ000).
It is. The reflection center wavelengths of the narrow-band variable optical decoders 31, 41, 51 are 1547.40 nm, 1547.72 nm, and 1548.04 nm, respectively. The image of the optical fiber core refractive index modulation of the narrow-band optical encoder used in the present embodiment has the same structure as in FIG. 4, the unit segment length is about 2.4 mm, and the length of the unit diffraction grating is the unit segment. Same as the length. The refractive index modulation periods Λ of the diffraction gratings of the narrow-band variable optical decoders 31, 41, 51 were about 534.7 nm, about 534.8 nm, and about 534.9 nm, respectively.

  In the present embodiment, the narrowband variable optical decoder 31 has a narrowband optical decoder 31C having the characteristics shown in FIG. 5C and a narrowband optical decoder 31A having the characteristics shown in FIG. In the wavelength setting unit 33, the narrowband optical decoder to be used is set to either the narrowband optical decoder 31C or the narrowband optical decoder 31A. Similarly, the narrowband variable optical decoder 41 includes a narrowband optical decoder 41A having the characteristics shown in FIG. 5A and a narrowband optical decoder 41B having the characteristics shown in FIG. The setting unit 43 sets the narrowband optical decoder to be used to either the narrowband optical decoder 41A or the narrowband optical decoder 41B. Similarly, the narrowband variable optical decoder 51 includes a narrowband optical decoder 51B having the characteristics shown in FIG. 5B and a narrowband optical decoder 51C having the characteristics shown in FIG. The setting unit 53 sets the narrowband optical decoder to be used to either the narrowband optical decoder 51B or the narrowband optical decoder 51C.

  The narrowband variable optical decoder 31 receives an encoded chip pulse train S2CA having one or more wavelengths, an encoded chip pulse train S2AB having one or more wavelengths, and an encoded chip pulse train S2BC having one or more wavelengths. Is done. The narrowband variable optical decoder 31 outputs the encoded chip pulse train S3A or S3C having the wavelength set by the wavelength setting unit 33 (wavelength determined in advance by a reception contract or the like) to the receiver 32.

  The narrowband variable optical decoder 41 receives an encoded chip pulse train S2CA having one or more wavelengths, an encoded chip pulse train S2AB having one or more wavelengths, and an encoded chip pulse train S2BC having one or more wavelengths. Is done. The narrow-band variable optical decoder 41 outputs the encoded chip pulse train S3A or S3B having the wavelength set by the wavelength setting unit 43 (a wavelength predetermined by a reception contract or the like) to the receiver 42.

  The narrowband variable optical decoder 51 receives an encoded chip pulse train S2CA having one or more wavelengths, an encoded chip pulse train S2AB having one or more wavelengths, and an encoded chip pulse train S2BC having one or more wavelengths. Is done. The narrow-band variable optical decoder 51 outputs the encoded chip pulse train S3B or S3C having the wavelength set by the wavelength setting unit 53 (a wavelength predetermined by a reception contract or the like) to the receiver 52.

<< 3 >> Operation of the Embodiment FIGS. 6A to 6C are diagrams showing the encoded waveforms of the broadband optical encoders 14a, 14b, and 14c of the optical signal division multiplexing apparatus 10 shown in FIG. In the present embodiment, encoded pulse trains of three different optical signal input pulse widths of 20 ps by one broadband optical encoder 14a, 14b, 14c are shown. 6A to 6C, encoded pulse trains of optical signals having three wavelengths WA, WB, and WC have substantially the same shape. This indicates that each of the broadband optical encoders 14a, 14b, and 14c encodes a plurality of optical signals having different wavelengths with the same code.

  7A to 7C are diagrams showing the decoded waveforms (autocorrelation waveforms) of the narrow-band variable optical decoders 31, 41, 51 of the user side devices 30, 40, 50 shown in FIG. . FIG. 7A shows a decoded waveform (autocorrelation waveform) by a narrowband optical decoder for wavelength WA (in FIG. 2, narrowband optical decoder 31A or 41A). FIG. 7B shows a decoded waveform (autocorrelation waveform) by a narrowband optical decoder for wavelength WB (in FIG. 2, narrowband optical decoder 41B or 51B). FIG. 7C shows a decoded waveform (autocorrelation waveform) by a narrowband optical decoder for wavelength WC (in FIG. 2, narrowband optical decoder 51C or 31C). As shown in FIGS. 7A to 7C, the autocorrelation waveforms of the three different optical signals by the narrowband variable optical decoders 31, 41, 51 are handled by the respective narrowband optical decoders. An optical signal having a wavelength corresponding to the wavelength is reproduced.

  FIGS. 8A and 8B are diagrams when the chip pulse trains of the wavelength WB and the wavelength WC are decoded by the narrowband optical decoder for the wavelength WA (in FIG. 2, the narrowband optical decoder 31A or 41A). It is a figure which shows a cross correlation waveform. The light intensity of the cross-correlation waveform shown in FIGS. 8A and 8B is normalized by the peak value of the autocorrelation waveform of the optical signal having the wavelength WA shown in FIG. 7A. As described above, the peak value of the cross-correlation waveform shown in FIGS. 8A and 8B is sufficiently smaller than the peak value of the autocorrelation waveform of the optical signal having the wavelength WA in FIG. The autocorrelation waveform of the optical signal having the wavelength WA in a) can be easily distinguished by threshold processing.

  FIGS. 9A and 9B show a case where a chip pulse train of wavelengths WA and WC is decoded by a narrowband optical decoder for wavelength WB (in FIG. 2, narrowband optical decoder 41B or 51B). It is a figure which shows a cross correlation waveform. 9A and 9B is normalized by the peak value of the autocorrelation waveform of the optical signal having the wavelength WB in FIG. 7B. As described above, the peak value of the cross-correlation waveform shown in FIGS. 9A and 9B is sufficiently smaller than the peak value of the autocorrelation waveform of the optical signal having the wavelength WB in FIG. The autocorrelation waveform of the optical signal having the wavelength WB of b) can be easily distinguished by threshold processing.

  FIGS. 10A and 10B show a case where a chip pulse train of wavelength WA and wavelength WB is decoded by a narrowband optical decoder for wavelength WC (in FIG. 2, narrowband optical decoder 51C or 31C). It is a figure which shows a cross correlation waveform. The light intensity of the cross-correlation waveform shown in FIGS. 10A and 10B is normalized by the peak value of the autocorrelation waveform of the optical signal having the wavelength WC in FIG. 7C. As described above, the peak value of the cross correlation waveform shown in FIGS. 10A and 10B is sufficiently smaller than the peak value of the autocorrelation waveform of the optical signal having the wavelength WC in FIG. The autocorrelation waveform of the optical signal having the wavelength WC of c) can be easily distinguished by threshold processing.

<< 4 >> Effects of the Embodiment As described above, according to the present embodiment, a plurality of user sides from the optical signal division multiplexing apparatus 10 which is a facility on the office side, such as video distribution of a subscriber system, etc. When data is distributed to the devices 30, 40, and 50, the wavelength is allocated for each channel, and the user-side devices 30, 40, and 50 are allocated for each code. In this way, each of the user side devices 30, 40, 50 does not receive unnecessary channel data, and a plurality of channel signals (physically required by the user side devices 30, 40, 50) ( For example, it is possible to receive a channel signal having a wavelength corresponding to a channel for which reception is contracted, and select a desired wavelength channel by the wavelength setting unit.

  In addition, according to the present embodiment, since the broadband optical encoder that can simultaneously encode the optical signals of a plurality of wavelength channels into the same code is used, the broadband optical encoder converts the FBG encoder into a plurality of wavelength channels. One is sufficient. Therefore, compared to the conventional configuration in which one pair of FBG encoder and FBG decoder needs to be prepared for each wavelength channel, the cost per channel can be reduced and the mounting area of the FBF encoder can be reduced. .

<< 5 >> Modification In the above description, the case where the periodic refractive index modulation structure formed by forming the Bragg diffraction grating in the core of the optical fiber is applied to the optical encoder and the optical decoder has been described. However, a periodic refractive index modulation structure other than the Bragg diffraction grating may be applied to the optical encoder and optical decoder.

  10 optical signal division multiplexing device (transmission side device), 11 pulse signal generator, 11a, 11b, 11c pulse generator, 12 optical modulator (modulated optical pulse output unit), 12a, 12b, 12c optical modulator, 13 selection 13a, 13b, 13c splitter, 14a, 14b, 14c wideband optical encoder, 15 coupler, 21 optical cable, 22 splitter, 30, 40, 50 user side device (receiving side device), 31, 41, 51 narrowband Variable optical decoder, 32, 42, 52 Optical receiver, 33, 43, 53 Wavelength setting unit, 61 Optical fiber, 62 Unit diffraction grating, 63 Core, 64 Phase shift unit, 65 Diffraction grating, WA, WB, WC Wavelength S0A Pulse signal with wavelength WA, S0B Pulse signal with wavelength WB, S0C Pulse signal with wavelength WC S1A modulated optical pulse signal of wavelength WA, S1B modulated optical pulse signal of wavelength WB, S1C modulated optical pulse signal of wavelength WC, S2CA multiplexed chip pulse train of wavelength WC and encoded chip pulse train of wavelength WA, S2AB Encoded chip pulse train of multiplexed wavelength WA and encoded chip pulse train of wavelength WB, S2BC Encoded chip pulse train of wavelength WB and encoded chip pulse train of wavelength WC, S3A Decoded waveform of wavelength WA (self Correlation waveform), S3B decoded waveform (autocorrelation waveform) of wavelength WB, S3C decoded waveform (autocorrelation waveform) of wavelength WC.

Claims (6)

A modulated optical pulse output unit that outputs a plurality of modulated optical pulse signals having different wavelengths;
A selector that generates and outputs a plurality of bundles of optical signals including one or more modulated optical pulse signals having a wavelength selected from the plurality of modulated optical pulse signals;
A plurality of broadband optical encoders respectively corresponding to the bundle of optical signals;
Each of the plurality of wideband optical encoders encodes one or more modulated optical pulse signals included in a corresponding bundle of optical signals in the bundle of optical signals, and one or more coding chips Output a pulse train,
An optical signal division multiplexing apparatus, further comprising: a multiplexing unit that multiplexes the one or more encoded chip pulse trains output from each of the plurality of broadband optical encoders. Each of the plurality of broadband optical encoders includes:
An optical waveguide;
A plurality of periodic refractive index distribution structures formed in the optical waveguide and arranged in the waveguide direction of the optical waveguide;
The phase shift unit, which is provided between the plurality of periodic refractive index distribution structure units and shifts the phase of any one of the chip pulses constituting the encoded chip pulse train. Optical signal division multiplexing apparatus. Each of the plurality of broadband optical encoders includes:
The plurality of periodic refractive index distribution structures are a plurality of unit diffraction gratings,
Determine a plurality of unit segments that are sections of the optical waveguide divided into lengths equal to the waveguide direction, and one of the plurality of unit diffraction configurations is disposed in each of the plurality of unit segments,
The unit diffraction grating length is Lg,
The length in the waveguide direction of one unit segment is Ls,
When the number of modulated optical pulse signals of different frequencies encoded by each of the plurality of broadband optical encoders is Nw,
Lg ≦ Ls / Nw
The optical signal division multiplexing apparatus according to claim 1 or 2, wherein: A transmission-side device that outputs the multiplexed optical signal to the transmission line; and
In an optical signal division multiplex transmission system comprising: a plurality of receiving side devices that receive the multiplexed optical signal through the transmission path;
The transmitting device is the optical signal division multiplexing device according to any one of claims 1 to 3,
The plurality of receiving side devices correspond to any of the plurality of wideband optical encoders,
Each of the plurality of receiving side devices has a narrowband variable optical decoder having a decodable band narrower than a codeable band of the corresponding wideband optical encoder,
The narrowband variable optical decoder receives the multiplexed one or more encoded chip pulse trains, selects a wavelength of an optical signal to be decoded, and is selected from the one or more encoded pulse signals An optical signal division multiplex transmission system comprising means for decoding a wavelength-encoded pulse signal. Outputting a plurality of modulated optical pulse signals having different wavelengths;
Generating and outputting a plurality of bundles of optical signals including one or more modulated optical pulse signals having a wavelength selected from the plurality of modulated optical pulse signals; and
Each of the plurality of broadband optical encoders corresponding to each of the plurality of optical signal bundles encodes one or more modulated optical pulse signals included in the corresponding optical signal bundle of the plurality of optical signal bundles. And outputting one or more encoded chip pulse trains;
And a step of multiplexing the one or more encoded chip pulse trains output from each of the plurality of wideband optical encoders. An optical signal division multiplex transmission method for transmitting a plurality of multiplexed encoded chip pulse trains from a transmission side device through a transmission path to a plurality of reception side devices,
In the transmission side device,
Output multiple modulated optical pulse signals with different wavelengths,
Generating a plurality of bundles of optical signals including one or more modulated optical pulse signals having a wavelength selected from the plurality of modulated optical pulse signals;
Each of the plurality of broadband optical encoders corresponding to each of the plurality of optical signal bundles encodes one or more modulated optical pulse signals included in the corresponding optical signal bundle of the plurality of optical signal bundles. Output one or more encoded chip pulse trains,
Multiplexing the one or more encoded chip pulse trains output from each of the plurality of broadband optical encoders;
In each of the plurality of receiving side devices,
Receiving the multiplexed one or more encoded chip pulse trains;
Select the wavelength of the optical signal to decode,
An optical signal division multiplex transmission method, comprising: decoding an encoded pulse signal having a wavelength selected from the one or more encoded pulse signals.

Images