JP2007318219A - Optical label recognition method, optical label recognition apparatus, and optical label switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to recognize an optical label at a speed faster than heretofore. <P>SOLUTION: The optical label recognition method includes: a step of receiving an optical label wherein first to N-th spread pulses obtained by applying processing of coding an (N-m+1)th bit of an original optical signal by an m-th code to first to N-th bits are arranged in this order; a step of branching the optical label to first to N-th branch optical label; a step of decoding an m-th spread pulse located at the order equal to a number m of an m-th branch optical label; a forth step of generating first to N-th electric signals being binary electric signals obtained by applying photoelectric conversion to an m-th decoded optical signal; and a step of reading the binary electric signals from the first to N-th electric signals by using a local clock signal, thereby recognizing the arrangement of the read binary electric signals as the optical label. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical label recognition method, an optical label recognition device, and an optical label switch including the optical label recognition device.

  In recent years, with the development of data communication represented by the Internet, an increase in communication speed has been demanded. For this reason, attention has been paid to an optical network that performs communication using an optical signal instead of a conventional communication network using an electrical signal.

  One of the causes that hinders the speedup in the optical network is that the optical label recognition of the optical packet at the node is slow. That is, in the prior art, in order to identify the address of the optical label and route the optical packet to this address, it is necessary to photoelectrically convert the optical label into an electrical signal having a low processing speed. And based on the electrical signal of the optical label photoelectrically converted, the electrical control switching was performed.

Therefore, various proposals have been made to perform optical label recognition at higher speed. For example, a single pulse light (optical clock pulse) synchronized with the first bit of the optical label is generated in an optical label recognizer, and the optical label is batch-converted in parallel using this optical clock pulse. There has been proposed a method of performing optical label recognition by photoelectrically converting (see, for example, Patent Document 1).
JP 2005-64871 A

  However, the method of Patent Document 1 needs to perform O / E / O conversion (optical / electrical / optical conversion) when generating an optical clock pulse. Therefore, a time difference of about several tens of ns occurs between the reception time of the first bit of the optical label and the generation time of the optical clock pulse. As a result, there is a problem that the optical label recognition process is delayed by the time difference.

  Further, in the method of Patent Document 1, it is necessary to provide both an electric pulse generator and an optical pulse generator in order to generate an optical clock pulse. Therefore, there is a problem that the system configuration becomes complicated.

  The present invention has been made in view of such problems.

  As a result of earnest research, the inventor has used the local clock signal generated by the optical label recognition apparatus to wait for the input of the optical label and generate an optical clock pulse at a higher speed than the method of Patent Document 1. Recognizing that recognition can be performed, the present invention has been completed.

  Accordingly, an object of the present invention is to provide an optical label recognition method and an optical label recognition apparatus which can perform optical label recognition at a higher speed than before by using a local clock signal, and which has a simpler system configuration than the conventional one. And an optical label switch using the optical label recognition device.

  In order to solve the above-described problem, the optical label recognition method according to the first aspect of the present invention includes five steps.

  First, an N-bit original light signal (where N is an integer of N ≧ 2) and different first to Nth codes are prepared.

  In the first step, an encoding process for encoding the (N−m + 1) th bit of the original light signal (where m is an integer of 1 ≦ m ≦ N) with the mth code is performed as the first to Nth bits. The first to Nth diffusion pulses obtained by performing each of the optical labels receive optical labels arranged on the time axis in a certain cycle and in this order without overlapping each other.

  In the second step, the received optical labels are branched into N to generate first to Nth branched optical labels.

  In the third step, the m-th decoded light is decoded by decoding the m-th spread pulse located in the same order as the number m of the m-th branch light label among the first to N-th spread pulses included in the m-th branch light label. By performing a signal generation process for each of the first to Nth branch optical labels, first to Nth decoded optical signals including either or both of an autocorrelation optical signal and a cross correlation optical signal are generated.

  In the fourth step, a process of generating an m-th electrical signal that is a binary electrical signal obtained by photoelectrically converting the m-th decoded optical signal with a threshold value between the intensity of the autocorrelation optical signal and the intensity of the cross-correlation optical signal Is performed for each of the first to Nth decoded optical signals to generate the first to Nth electrical signals.

  In the fifth step, binary electrical signals are read in this order from the first to Nth electrical signals using a local clock signal that is shorter than the cycle of the diffusion pulse and asynchronous.

  Then, the read sequence of binary electrical signals is recognized as an optical label.

  This optical label recognition method is an application of optical code division multiplexing (OCDM).

  The optical label includes N diffusion pulses (first to Nth diffusion pulses) arranged at a constant period on the time axis. The spread pulse is obtained by encoding the first bit of the N-bit original optical signal with the first code, the second bit with the second code, and the like in the same manner, by encoding the Nth bit with the Nth code. Generated. Here, the N codes used for encoding are different from each other.

  After this optical label is received, it is branched into first to Nth branch optical labels. Then, the first spreading pulse is decoded by the first branching optical label, the second spreading pulse by the second branching optical label, and the Nth spreading pulse by the Nth branching optical label. An Nth decoded optical signal is generated. The first to Nth decoded optical signals include either or both of an autocorrelation optical signal and a cross correlation optical signal.

  Subsequently, the first to Nth decoded optical signals are photoelectrically converted using the intensity between the autocorrelation optical signal and the cross-correlation optical signal as a threshold value, and first to Nth electrical signals including a binary electrical signal are generated.

  That is, the first electric signal includes a binary electric signal corresponding to the first diffusion pulse of the optical label. The second electric signal includes a binary electric signal corresponding to the second diffusion pulse of the optical label. Similarly, the Nth electrical signal includes a binary electrical signal corresponding to the Nth diffusion pulse of the optical label.

  The binary electric signals carried on the first to Nth electric signals are read in this order using the local clock signal as a read clock. The array of binary electrical signals read out in this way is recognized as an optical label.

  Here, the local clock signal is a clock signal that gives the read timing of the binary electric signal and is generated (asynchronously) irrespective of the optical label. In order to accurately read out the binary electric signal included in the electric signal, the local clock signal has a shorter period and is asynchronous than the period of the diffusion pulse. Note that “asynchronous” means that an integer multiple of the period of the local clock does not match the period of the diffusion pulse.

  As a more preferred embodiment, in the fourth step, when the mth decoded optical signal does not include an autocorrelation optical signal, the first voltage from the start point to the end point of the mth decoded optical signal is photoelectrically converted to the first voltage. m An electrical signal is generated. When the m-th decoded optical signal includes an autocorrelation optical signal, the first voltage from the start point to the autocorrelation optical signal and the second voltage different from the first voltage from the autocorrelation optical signal to the end point In addition, it is preferable to generate the m-th electrical signal obtained by photoelectric conversion.

  Furthermore, in the fifth step, the arrangement of the first and second voltages read in this order is recognized as an optical label by a local clock signal one cycle before the end point of the first to Nth electrical signals. It is preferable.

  In this embodiment, when generating the first to Nth electrical signals, if the mth decoded optical signal includes an autocorrelation optical signal, the process proceeds from the start point of the mth decoded optical signal to the autocorrelation optical signal. The first voltage and from the autocorrelation optical signal to the end point of the decoded optical signal are converted into the second voltage.

  That is, in photoelectric conversion, the auto-correlation optical signal is sampled and held. As a result, the generated mth electrical signal has a waveform in which the first voltage from the start point to the autocorrelation optical signal is the first voltage, and the second voltage is from the autocorrelation optical signal to the end point of the mth electrical signal. It becomes.

  If the mth decoded optical signal does not include an autocorrelation optical signal, an mth electrical signal is generated by photoelectrically converting the first voltage from the start point to the end point of the mth decoded optical signal.

  Then, the arrangement of the first and second voltages is read out from the first to Nth electrical signals with a local clock signal. Specifically, from the end point of the first to Nth electrical signals, the voltage (the first voltage and the first voltage) in this order from the first to Nth electrical signals at a time point one cycle before the period of the local clock signal. 2 voltage). Then, the arrangement of the first voltage (corresponding to “0” of the binary signal) and the second voltage (corresponding to “1” of the binary signal) reproduces the information included in the optical label. That is, the optical label is recognized.

  An optical label recognition device according to a second aspect of the present invention includes a receiving unit, a branching unit, a decoding device, a photoelectric conversion unit, a local clock generation device, and a bit operation unit.

  The receiving unit uses the N-bit original light signal prepared in advance (where N is an integer of N ≧ 2) and the first to Nth codes different from each other, and (N−m + 1) th of the original light signal. The first to Nth spreading pulses obtained by performing the encoding process for encoding the bit (where m is an integer of 1 ≦ m ≦ N) with the mth code for each of the first to Nth bits The optical labels arranged on the time axis in a predetermined cycle and in this order are received without overlapping each other.

  The branching unit branches the received optical labels into N to generate first to Nth branched optical labels.

  The decoding apparatus decodes the m-th decoded light by decoding the m-th spread pulse located in the same order as the number m of the m-th branch optical label among the first to N-th spread pulses included in the m-th branch optical label. By performing a signal generation process for each of the first to Nth branch optical labels, first to Nth decoded optical signals including either or both of an autocorrelation optical signal and a cross correlation optical signal are generated.

  The photoelectric conversion unit generates a m-th electrical signal that is a binary electrical signal obtained by photoelectrically converting the m-th decoded optical signal with a threshold value between the intensity of the autocorrelation optical signal and the intensity of the cross-correlation optical signal. Is performed for each of the first to Nth decoded optical signals to generate the first to Nth electrical signals.

  The local clock generator generates a local clock signal having a period shorter than that of the spread pulse and asynchronous.

  The bit operation unit reads the binary electric signal in this order from the first to Nth electric signals using the local clock signal.

  As described above, according to this optical label recognition device, the binary electrical signal read out in this order from the first to Nth electrical signals is a local clock signal generated asynchronously with the optical label. Can be recognized as an optical label.

  An optical label switch according to a third aspect of the present invention uses the above-described optical label recognition device. The optical label switch includes a packet branching unit, an optical label recognition device, a control signal generation unit, and an optical switch.

  The packet branching unit receives an optical packet composed of an optical label and a payload, and separates it into an optical label and a payload.

  The optical label recognition device recognizes an optical label.

  The control signal generation unit generates a control signal based on the recognized optical label.

  The optical switch branches the destination of the payload based on the control signal.

  As described above, the optical label switch includes the above-described optical label recognition device as a component, and thus can perform optical label recognition at a higher speed than in the past.

  According to the optical label recognition method and the optical label recognition apparatus of the present invention, the optical label recognition can be performed at a higher speed than before by using the local clock signal. In addition, the system configuration can be simplified as compared with the prior art.

  As a result, the optical label switch including the optical label recognition device of the present invention as a component can perform optical packet routing at a higher speed than the conventional one.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is only a schematic illustration of each component to the extent that the present invention can be understood. The embodiments described below are merely preferred examples. Therefore, the present invention is not limited to the following embodiment.

  The structure and operation of the optical label switch will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the overall structure of an optical label switch.

  The optical label switch 10 includes a packet branching unit 12, an optical label recognition device 14, a control signal generation unit 16, and an optical switch 18.

  The optical packet P is transmitted to the optical label switch 10 via the transmission path 20. The optical packet P is an optical signal with the optical label p2 added to the head of the payload p1. The payload p1 stores data to be transmitted. The optical label p2 stores the destination of the payload p1 (transmission destination address).

  Although details will be described later, the optical label p2 includes first to fourth diffusion pulses DS1 to DS4 arranged on the time axis in a certain cycle and in this order without overlapping each other (FIG. 2).

  The packet branching unit 12 branches the optical packet P into a payload p1 and an optical label p2. The payload p1 and the optical label p2 constituting the optical packet P have different light wavelengths. The packet branching unit 12 branches the payload p1 to the optical switch 18 and the optical label p2 to the optical label recognizing device 14 using the difference in wavelength.

  The optical label recognition device 14 recognizes information included in the optical label p2 and converts the recognized information into an electric pulse signal. The optical label recognition device 14 will be described later.

  The control signal generator 16 generates a control signal for controlling the optical switch 18 based on the electric pulse signal generated by the optical label recognition device 14. Then, this control signal is transmitted to the optical switch 18.

  The optical switch 18 receives the control signal described above. Then, optical switching is performed by a control signal. That is, based on the control signal, a transmission path for transmitting the payload p1 is selected.

  Next, the generation process (encoding process) of the optical label p2 input to the optical label switch 10 will be described with reference to FIG. FIG. 2 is a schematic diagram showing a schematic configuration of an optical label encoding device.

  In the encoding device 32, the optical label p2 is generated by encoding the original original optical signal by the OCDM method. More specifically, the optical label p2 is encoded bit by bit with the first to Nth codes (M-sequence code string: described later) different from each other with respect to the original optical signal that is an N-bit optical pulse. To generate.

  First, the encoding process will be described by taking as an example the case where the original optical signal is a 4-bit optical pulse represented by “1010”.

The encoding device 32 used for encoding the optical label p2 includes first to fourth encoding units EP1 to EP4, transmission paths TL1 to TL4, a multiplexer 34, and a transmission path TL _out .

  The number of these encoding units is the same as the number of bits of the original optical signal (four), and therefore the first to fourth encoding units EP1 to EP4 are arranged in parallel. As will be described in detail later, an encoder en1 included in the first encoder EP1, an encoder en2 included in the second encoder EP2, an encoder en3 included in the third encoder EP3, and a fourth code Encoders en4 provided in the conversion unit EP4 have different M-sequence code strings. Here, the M-sequence code string indicates a random number in which binary numbers “0” and “1” are arranged at random.

Transmission lines TL _in 1 to TL _in 4 are connected to the first to fourth encoding units EP1 to EP4 _{in a} one-to-one relationship, respectively.

Each of the transmission line _{TL in 1~TL} in 4 is encoded before the original optical signal ( "1010") is transmitted by being separated for each bit. Hereinafter, the optical pulses obtained by separating the original light signal for each bit are referred to as first to fourth original light pulses Pls1 to Pls4.

More specifically, the first original light pulse Pls1 (“1”) corresponding to the fourth bit of the optical label p2 “1010” is input to the first encoding unit EP1 from the transmission line TL _in 1. From the transmission line TL _in 2, the second original optical pulse Pls2 (“0”) corresponding to the third bit of the optical label p2 is input to the second encoding unit EP2. From the transmission line TL _in 3, the third original optical pulse Pls3 (“1”) corresponding to the second bit of the optical label p2 is input to the encoding unit EP3. From the transmission line TL _in 4, a fourth original light pulse Pls4 (“0”) corresponding to the first bit of the optical label p2 is input to the fourth encoding unit EP4.

  That is, the mth original light pulse Plsm corresponding to the (N−m + 1) th bit of the original light signal (where m is an integer satisfying 1 ≦ m ≦ N) is input to the mth encoding unit EPm. .

  Also, transmission lines TL1 to TL4 are connected to the first to fourth encoding units EP1 to EP4, respectively, in a one-to-one relationship. The lengths of the transmission lines TL1 to TL4, that is, the optical path lengths are set so as to increase in this order. Therefore, the delay time of optical signal transmission in the transmission lines TL1 to TL4 becomes longer in this order.

  Here, the delay time increment ΔT (1,2) between the transmission lines TL1 and TL2, the delay time increment ΔT (2,3) between the transmission lines TL2 and TL3, and the transmission lines TL3 and TL4. The delay time increments ΔT (3, 4) between the two are set to a constant value ΔT (ΔT (1,2) = ΔT (2,3) = ΔT (3,4) = ΔT).

  The first original light pulse Pls1 encoded by the first encoding unit EP1 is output to the transmission line TL1 as the first spreading pulse DS1. The second original light pulse Pls2 encoded by the second encoding unit EP2 is output to the transmission line TL2 as the second spread pulse DS2. The third original light pulse Pls3 encoded by the third encoding unit EP3 is output to the transmission line TL3 as the third spread pulse DS3. The fourth original light pulse Pls4 encoded by the fourth encoding unit EP4 is output to the transmission line TL4 as the fourth spread pulse DS4.

The multiplexer 34 has an input port and an output port. Transmission lines TL1, TL2, TL3, and TL4 are connected to the input port. Further, a transmission line TL _out is connected to the output port.

  Accordingly, in the multiplexer 34, the first to fourth diffusion pulses DS1 to DS4 are combined. By the way, as already described, the transmission lines TL1 to TL4 are set so that the delay time is increased by ΔT in this order. ΔT is set to be longer than the duration of the first to fourth diffusion pulses DS1 to DS4. As a result, at the output port of the multiplexer 34, the first to fourth spread pulses DS1, DS2, DS3, and DS4 are arranged on the time axis in this order with a constant period ΔT without overlapping each other. Are arranged and output.

In this way, the optical label p2 is generated. The optical label p2 is an optical pulse in which the first to fourth diffusion pulses DS1, DS2, DS3, and DS4 are arranged in time series. Here, the period ΔT of the first to fourth diffusion pulses DS1 to DS4 is also referred to as a “diffusion pulse period”. The optical label p2 is transmitted to the transmission line TL _out .

The transmission line TL _out is connected to the multiplexer 36. In this multiplexer 36, the optical label p2 and the payload p1 are combined at the same timing, and the optical packet P is generated. Then, the optical packet P is transmitted to the optical label switch 10 through the transmission path 20.

  Next, the details of the first to fourth encoding units EP1 to EP4 will be described with reference to FIG. FIG. 3 is a schematic diagram showing a schematic configuration of the encoding unit EP1.

  The first to fourth encoding units EP1 to EP4 have the same structure and operation except for the M-sequence code strings of the encoders en1 to en4. Therefore, in the following description, the first encoding unit EP1 is extracted from the first to fourth encoding units EP1 to EP4 as a representative, and the structure and operation will be described in detail.

  Referring to FIG. 3, the first encoding unit EP1 includes a circulator 38 and an encoder en1.

  The circulator 38 includes a first port 38a, a second port 38b, and a third port 38c.

  The first original light pulse Pls 1 (“1”) corresponding to the fourth bit of the optical label p 2 (“1010”) is input to the first port 38 a of the circulator 38. The first original light pulse Pls1 input to the first port 38a is introduced into the encoder en1 via the second port 38b of the circulator 38. The first original light pulse Pls1 introduced into the encoder en1 is spread on the time axis by the encoder en1 to become a first spread pulse DS1, and is fed back to the second port 38b. The returned first spread pulse DS1 is transmitted to the transmission line TL1 via the third port 38c of the circulator 38.

  The encoder en1 includes a fiber grating G (i) (i = 1, 2,..., P) arranged in series in a p-chip along a length direction of one linear optical fiber. , Phase shift sections PS (j) (j = 1, 2,...) Provided between adjacent fiber gratings G (k) and G (k + 1) (k = 1, 2,..., P−1). ., P-1).

  In this example, the fiber gratings G (i) are arranged in series so as to be separated from the circulator 38 as the subscript i increases.

  Each of the fiber gratings G (i) has an equal width (length along the optical fiber) and an equal Bragg reflection wavelength. The fiber grating G (i) is formed, for example, by periodically changing the refractive index of the core of the optical fiber.

The phase shift unit PS (j) is configured as an interval provided between adjacent fiber gratings G (k) and G (k + 1). Specifically, the interval of the phase shift unit PS (j) is a phase π / 2 or a width corresponding to the phase π, depending on a code used for encoding (M sequence code string _Me 1: described later). (Length along the optical fiber). That is, the first original light pulse Pls1 introduced into the encoder en1 is subjected to a phase shift of π / 2 or π every time it propagates through the phase shift unit PS (j).

  Incidentally, the first original light pulse Pls1 reciprocates through the encoder en1. As a result, the first original light pulse Pls1 undergoes a phase shift of π in a reciprocating manner by the phase shift unit PS (j) having a width corresponding to the phase π / 2. Similarly, the first original light pulse Pls1 is reciprocally subjected to a phase shift of 2π (= 0) by the phase shift unit PS (j) having a width corresponding to the phase π.

Hereinafter, as an example, a case where an M-sequence code string M _e 1 (0001111101011001) (hereinafter also simply referred to as a code string M _e 1) having a code length of 15 is applied to the encoder en1 will be described.

In this case, the total chip number p of the fiber grating G (i) is equal to the code length of the code string M _e 1 and is 15. As shown in FIG. 3, the individual fiber gratings G (1), G (2), G (3), G (4),..., G (14) and G (15) are represented by a code string M. each code 0,0,0,1 of _e 1, · · ·, 0 and 1, corresponding respectively one-to-one.

  The phase shift unit PS (j) has a phase π / 2 when the value changes between adjacent fiber gratings G (k) and G (k + 1), that is, when “0 → 1” or “1 → 0”. Set to the corresponding width.

  The phase shift unit PS (j) corresponds to the phase π when the adjacent fiber gratings G (k) and G (k + 1) have the same value, that is, “0 → 0” or “1 → 1”. Set to the width you want.

  Therefore, the phase shift amount (one way) of each phase shift unit PS (j) is PS (1) = π, PS (2) = π, PS (3) = π / 2, as shown in FIG. PS (4) = π, PS (5) = π, PS (6) = π, PS (7) = π / 2, PS (8) = π / 2, PS (9) = π / 2, PS ( 10) = π / 2, PS (11) = π, PS (12) = π / 2, PS (13) = π, and PS (14) = π / 2.

When the first original light pulse Pls1 is introduced into the encoder en1 having such a code string M _e 1, the first original light pulse Pls1 is reflected by the respective fiber gratings G (i). The reflected light pulses (hereinafter referred to as reflected light pulses) interfere with each other, so that each reflected light pulse has a phase difference (0, 0, 0, π, π, π, π, 0, π, The first diffusion pulse DS1 arranged in time series at 0, π, π, 0, 0, π) is obtained.

  Next, the configuration and operation of the optical label recognition device 14 will be described with reference to FIG. FIG. 4 is a schematic diagram showing a schematic configuration of the optical label recognition apparatus together with signals obtained by the respective components.

  The optical label recognition device 14 includes a branching unit 22, a decoding device 24, a photoelectric conversion device 26, a local clock generation device 28, and a bit operation device 30.

  The branching unit 22 also serves as a receiving unit, and is connected to the transmission path 20. The branching unit 22 is composed of a known duplexer. The branching unit 22 branches the optical label p2 transmitted through the transmission path 20 into the same number of bits as the number of bits of the optical label p2, in this case, four to generate first to fourth branched optical labels sl1 to sl4. To do. Then, the branching unit 22 transmits these first to fourth branched optical labels sl1 to sl4 toward the decoding device 24.

  The decryption device 24 includes first to fourth decryption units DP1 to DP4. The first to fourth decoding units DP1 to DP4 decode the first to fourth branched optical labels sl1 to sl4, respectively. In this decoding, the diffusion pulse period ΔT does not change.

  That is, the first decoding unit DP1 decodes the first spread pulse DS1 (the fourth bit “1”) included in the first branched optical label sl1 to generate the first decoded optical signal DPls1. The second decoding unit DP2 decodes the second spread pulse DS2 (third bit “0”) included in the second branched optical label sl2 to generate a second decoded optical signal DPls2. The third decoding unit DP3 decodes the third spread pulse DS3 (second bit “1”) included in the third branch optical label sl3 to generate a third decoded optical signal DPls3. The fourth decoding unit DP4 decodes the fourth spread pulse DS4 (first bit “0”) included in the fourth branch optical label sl4 to generate a fourth decoded optical signal DPls4.

  Here, the decoding of the first to fourth spreading pulses DS1 to DS4 will be described in detail with reference to FIG. FIG. 5 is a schematic diagram illustrating a schematic configuration of the decoding unit.

  The first to fourth decoding units DP1 to DP4 have the same structure and operation except that the M-sequence code strings of the decoders de1 to de4 are different. Therefore, in the following description, the first decoding unit DP1 is extracted as a representative from the first to fourth decoding units DP1 to DP4, and the structure and operation will be described in detail.

  The first decoding unit DP1 has substantially the same structure as the first encoding unit EP1 described above. That is, the first decoding unit DP1 includes a circulator 40 and a decoder de1.

  Since the circulator 40 has the same structure as the circulator 38 described above, the description thereof is omitted.

  Similar to the encoder en1, the decoder de1 includes p fiber gratings G ′ (i) arranged in series along a length direction of a single linear optical fiber, and an adjacent fiber. This is a structure provided with a phase shift section PS ′ (j) provided between the gratings G ′ (k) and G ′ (k + 1).

However, the M-sequence code string M _d 1 applied to the decoder de1 is an inversion of the M-sequence code string M _e 1 applied to the encoder en1. That is, in the decoder de1, the code string M _d 1 is (100110101111000).

This relationship is also established in the other decoders de2, de3, and de4. That is, the code sequence M _d 2 applied to the decoder de2 is an inversion of the code sequence M _e 2 applied to the encoder en2. The code string M _d 3 applied to the decoder de3 is obtained by inverting the code string M _e 3 applied at the encoder en3. The code string M _d 4 applied to the decoder de4 is obtained by inverting the code string M _e 4 applied by the encoder en4.

When the first branched optical label sl1 branched by the branching unit 22 is input to the decoder de1, the first decoded light in which only the first spread pulse DS1 encoded by the code string M _e 1 is decoded. A signal DPls1 is obtained (FIG. 4). That is, only the first diffusion pulse DS1 that holds the information (“1”) of the fourth bit of the first branch optical label sl1 among the first to fourth diffusion pulses DS1 to DS4 constituting the first branch optical label sl1. Is decrypted.

  More specifically, the first diffusion pulse DS1 is reflected by each fiber grating G '(i) while undergoing a phase shift by the phase shift unit PS' (j). As a result, the reflected first diffusion pulse DS1 is interfered and superimposed with each other relative phase difference to obtain a light peak (autocorrelation light signal) having a high intensity. Thereby, the first diffusion pulse DS1 is decoded.

On the other hand, the decoder de1 does not decode the second to fourth spread pulses DS2 to DS4. That is, the second to fourth spread pulse DS2~DS4 is encoded with code sequence _M e 2 to M _e 4. Therefore, even if the second to fourth spread pulses DS2 to DS4 pass through the decoder de1, only a light peak with a low intensity (cross-correlation optical signal) or a signal with an intensity of 0 (zero) can be obtained. .

  As a result of decoding by the decoder de1, a first decoded optical signal DPls1 having an autocorrelation optical signal at the position of the first spread pulse DS1 and a cross-correlation optical signal at the position of the third spread pulse DS3 is obtained.

  In the first decoded optical signal DPls1, the positions of the second and fourth diffusion pulses DS2 and DS4 are 0 in intensity. This is because the second and fourth original light pulses Pls2 and Pls4 corresponding to the second and fourth diffusion pulses DS2 and DS4 are “0”, respectively.

  That is, the first decoded optical signal DPls1 is time-sequentially with the spreading pulse period ΔT, and the autocorrelation optical signal (corresponding to DS1) → the intensity 0 signal (corresponding to DS2) → the cross correlation optical signal (corresponding to DS3) → intensity 0 It becomes an optical signal in which signals (corresponding to DS4) are arranged.

  Similarly to the first decoding unit DP1, the second decoding unit DP2 decodes only the second spread pulse DS2 (“0”) of the second branch optical label sl2 to obtain the second decoded optical signal DPls2. It is done. Specifically, the second decoded optical signal DPls2 has cross-correlation optical signals at the positions of the first and third diffusion pulses DS1 and DS3, and the intensity of the positions of the second and fourth diffusion pulses DS2 and DS4 is 0 (FIG. 4).

  In the third decoding unit DP3, only the third spread pulse DS3 (“1”) of the third branch optical label sl3 is decoded to obtain a third decoded optical signal DPls3. Specifically, the third decoded optical signal DPls3 has a cross-correlation signal at the position of the first diffusion pulse DS1, has an autocorrelation optical signal at the position of the third diffusion pulse DS3, and the second and fourth The intensity of the positions of the diffusion pulses DS2 and DS4 is 0 (FIG. 4).

  In the fourth decoding unit DP4, only the fourth spread pulse DS4 (“0”) of the fourth branched optical label sl4 is decoded to obtain a fourth decoded optical signal DPls4. Specifically, the fourth decoded optical signal DPls4 has cross-correlation optical signals at the positions of the first and third diffusion pulses DS1 and DS3, and the intensity of the positions of the second and fourth diffusion pulses DS2 and DS4 is 0 (FIG. 4).

  In summary, in the m-th decoding unit DPm, the first to N-th spread pulses DS1 to DSN included in the m-th branch optical label slm are positioned in the order equal to the number m of the m-th branch optical label. The mth spread pulse DSm is decoded to generate the mth decoded optical signal DPlsm.

  In this way, the decoding device 24 decodes the first spread pulse DS1 in the first branch optical label sl1, the second spread pulse DS2 in the second branch optical label sl2, and the third branch optical label sl3. The third spread pulse DS3 is decoded, and the first spread pulse DS4 is decoded in the fourth branched optical label sl4, and the first to fourth decoded optical signals DPls1 to DPls4 are obtained. These first to fourth decoded optical signals DPls 1 to DPls 4 are transmitted to the photoelectric conversion device 26.

  The photoelectric conversion device 26 includes first to fourth photoelectric conversion units OE1 to OE4. The first to fourth photoelectric conversion units OE1 to OE4 perform photoelectric conversion of the first to fourth decoded optical signals DPls1 to DPls4, respectively. Further, the first to fourth photoelectric conversion units OE1 to OE4 are provided when the photoelectrically converted first to fourth photoelectric conversion signals EL1 to EL4 (described later: FIG. 6) have an electric pulse having a predetermined intensity or more. Performs sample hold of the electrical pulse.

  Here, the configuration and operation of the first to fourth photoelectric conversion units OE1 to OE4 will be described in detail with reference to FIG. FIG. 6 is a schematic diagram illustrating a schematic configuration of the photoelectric conversion unit OE1.

  The first to fourth photoelectric conversion units OE1 to OE4 have the same structure. Therefore, in the following description, the first photoelectric conversion unit OE1 is extracted from the first to fourth photoelectric conversion units OE1 to OE4 as a representative, and the structure and operation will be described in detail.

  The first photoelectric conversion unit OE <b> 1 includes a photoelectric conversion circuit 42 and a sample hold circuit 44.

  The photoelectric conversion circuit 42 includes a photodiode or the like (not shown) and photoelectrically converts the first decoded optical signal DPls1 to generate a first photoelectric conversion signal EL1 corresponding to the first decoded optical signal DPls1. The photoelectric conversion circuit 42 performs photoelectric conversion so as not to change the diffusion pulse period ΔT of the first decoded optical signal DPls1.

  More specifically, the photoelectric conversion circuit 42 identifies whether the optical peak included in the first decoded optical signal DPls1 is an autocorrelation optical signal or a cross-correlation optical signal. For this discrimination, an intensity difference between the autocorrelation optical signal and the cross correlation optical signal (autocorrelation optical signal> cross correlation optical signal) is used.

  That is, in the photoelectric conversion circuit 42, a threshold value that is an intensity between the intensity of the autocorrelation optical signal and the intensity of the cross correlation optical signal is set in advance as a reference level for photoelectric conversion. Then, when the first decoded optical signal DPls1 includes an optical peak (autocorrelation optical signal) that is greater than or equal to the threshold value, the photoelectric conversion circuit 42 converts the optical peak into an electric pulse EPls1. That is, in the first decoded optical signal DPls1, the intensity of the optical peak is less than the threshold at a position other than the autocorrelation optical signal (the non-existence position of the autocorrelation optical signal and the presence position of the cross-correlation optical signal). The above-mentioned electric pulse is not generated.

  As a result of the photoelectric conversion by the photoelectric conversion circuit 42, the first photoelectric conversion signal EL1 becomes a signal having the electric pulse EPls1 only at the position of the first diffusion pulse DS1 (autocorrelation optical signal).

  The first photoelectric conversion signal EL1 is input to the sample hold circuit 44. When the first photoelectric conversion signal EL1 includes the above-described electric pulse EPls1, the first voltage (corresponding to “L” in FIG. 6) from the start point of the first photoelectric conversion signal EL1 to the electric pulse EPls1 is used. The first electric signal ES1 is generated by converting the electric pulse EPls1 to the end point of the first photoelectric conversion signal EL1 into a second voltage higher than the first voltage (corresponding to “H” in FIG. 6). To do.

  That is, the sample hold of the electric pulse EPls1 is performed. When the first photoelectric conversion signal EL1 does not include the electric pulse EPls1, the generated first electric signal ES1 is maintained at the first voltage in the entire section from the start point to the end point.

  By the way, the diffusion pulse period ΔT does not change between the first decoded optical signal DPls1 and the first photoelectric conversion signal EL1. Therefore, the above-described sample hold means that “from the start point of the first decoded optical signal DPls1 to the electric pulse EPls1 is converted to the first voltage, and from the electric pulse EPls1 to the end point of the first decoded optical signal DPls1 is set to the second voltage. It can also be said that the first electric signal ES1 is generated by conversion.

  Similarly to the first electric signal ES1, the second photoelectric conversion unit OE2 photoelectrically converts the second decoded optical signal DPls2 to generate a second photoelectric conversion signal EL2. Then, sample hold of the second photoelectric conversion signal EL2 is performed. As a result, the second electric signal ES2 (FIG. 4) in which the entire section from the start point to the end point is maintained at the first voltage is obtained.

  In the third photoelectric conversion unit OE3, the third decoded optical signal DPls3 is photoelectrically converted to generate a third photoelectric conversion signal EL3. Then, the sample hold of the third photoelectric conversion signal EL3 is performed. As a result, the first voltage from the start point of the third photoelectric conversion signal EL3 to the electric pulse EPls3 (not shown) existing at the position of the third diffusion pulse DS3 (autocorrelation optical signal) is maintained at the first voltage, and from the electric pulse EPls3. A third electrical signal ES3 (FIG. 4) is obtained in which the second voltage is maintained up to the end point of the third photoelectric conversion signal EL3.

  In the fourth photoelectric conversion unit OE4, the fourth decoded optical signal DPls4 is photoelectrically converted to generate a fourth photoelectric conversion signal EL4. Then, sample hold of the fourth photoelectric conversion signal EL4 is performed. As a result, a fourth electrical signal ES4 (FIG. 4) is obtained in which the entire interval from the start point to the end point of the fourth decoded optical signal DPls4 is maintained at the first voltage.

  These first to fourth electric signals ES <b> 1 to ES <b> 4 are transmitted to the bit arithmetic device 30.

  The local clock generator 28 includes a PLL (Phase Locked Loop) circuit (not shown), and generates a local clock signal. The period Δt of this local clock signal is smaller than the above-described diffusion pulse period ΔT (Δt <ΔT) and is asynchronous with the diffusion pulse period ΔT. Hereinafter, the period Δt is also referred to as “reading period”.

  The bit operation device 30 includes a bit operation circuit 46. The bit operation circuit 46 is connected to the first to fourth photoelectric conversion units OE1 to OE4. Further, a local clock signal is supplied from the local clock generator 28 to the bit operation circuit 46.

  The first to fourth electric signals ES <b> 1 to ES <b> 4 input to the bit operation circuit 46 are read at a read cycle Δt supplied from the local clock generator 28.

  The bit operation circuit 46 reads voltages (first voltage and second voltage) from the first to fourth electric signals ES1 to ES4 in the order of the electric signals ES1, ES2, ES3, and ES4 according to the local clock signal. And it arranges in time series in the read order. Here, the bit operation circuit 46 sets the first voltage to binary code “0” and the second voltage to binary code “1”.

  Then, the local clock signal one cycle before the point in time when any one or more of the first to fourth electric signals ES1 to ES4 changes from the second voltage to the first voltage (end point of the electric signal) ( The arrangement ("1010") of the first voltage ("0") and the second voltage ("1") read out in the shaded area in the figure is recognized as information having the optical label p2.

  Thereby, the optical label p2 is recognized. The optical label p2 recognized in this way is converted into an electric pulse signal and transmitted to the control signal generator 16.

  Hereinafter, the effect which the optical label recognition method of this embodiment and the optical label recognition apparatus 14 show | plays is demonstrated.

  As described above, in the optical label recognition method and the optical label recognition device 14 of this embodiment, the first to the first local clock signals are shorter than the spread pulse cycle supplied from the local clock generator 28 and are asynchronous. 4 Read the electrical signals ES1 to ES4. Therefore, it is possible to recognize the optical label p2 at a higher speed than in the prior art method in which an optical clock pulse is generated after waiting for the input of the optical label p2.

  According to the evaluation by the inventors, the optical label recognition apparatus of this embodiment is about several tens of ns faster than the case where an optical clock pulse synchronized with the first bit of the optical label is generated (background art). The optical label p2 can be recognized.

  Further, the optical label recognition method and the optical label recognition device 14 of this embodiment do not use the optical clock pulse generator that performs O / E / O conversion, which has been used in the prior art, so that the device configuration is simple. Become.

  Further, by using the optical label switch 10 using the optical label recognition method and the optical label recognition device 14 as a component of the node, the processing time required for branching the optical packet P and transmitting it to the next node is shortened. be able to.

  Next, the optical label recognition method and the design conditions of the optical label recognition device 14 of this embodiment will be described.

  In this embodiment, the sample and hold circuit 44 samples and holds the first electric pulse EPls1 corresponding to the autocorrelation optical signal included in the first photoelectric conversion signal EL1 (FIG. 6). However, if the bit arithmetic circuit 46 can read the electric pulses (for example, the first electric pulse EPls1) included in the first to fourth electric signals ES1 to ES4 without performing the sample hold, The sample hold circuit 44 does not need to be provided. However, in this case, it is necessary to provide a storage device in the bit arithmetic circuit 46 to store whether or not the first to fourth electric signals ES1 to ES4 include an electric pulse.

  The period Δt of the local clock signal generated by the local clock generator 28 is not particularly limited as long as it is smaller than the diffusion pulse period ΔT (Δt <ΔT) and asynchronous with the diffusion pulse period ΔT. However, in order to accurately read the first and second voltages from the electrical signals ES1 to ES4, it is preferable that Δt be about 1/10 to 1/8 of the diffusion pulse period ΔT.

The number p of fiber grating chips used in the encoder (decoder) is determined by the number N of bits of the original light pulse. That is, in order to assign an encoder having a different code to each bit of the original light pulse, it is desirable that the number of chips p is p ≧ log ₂ N.

It is a schematic diagram which shows the whole structure of an optical label switch. It is a schematic diagram which shows schematic structure of the encoding apparatus of an optical label. It is a schematic diagram which shows schematic structure of an encoding part. It is a schematic diagram which shows schematic structure of an optical label recognition apparatus. It is a schematic diagram which shows schematic structure of a decoding part. It is a schematic diagram which shows schematic structure of a photoelectric conversion part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical label switch 12 Packet branch part 14 Optical label recognition apparatus 16 Control signal generation part 18 Optical switch 20 Transmission path P Optical packet p1 Payload p2 Optical label EP1, EP2, EP3, EP4 Encoding part TL1, TL2, TL3, TL4 Transmission Line TL _out Transmission path en1, en2, en3, en4 Encoder TL _in 1, TL _in 2, TL _in 3, TL _in 4 Transmission path Pls1, Pls2, Pls3, Pls4 Original light pulse DS1, DS2, DS3, DS4 Spreading pulse 32 encoder 34 multiplexer 36 multiplexer 38 circulator 38a first port 38b second port 38c third port G (i) fiber grating PS (j) phase shift unit 22 branch unit 24 decoding device 26 photoelectric conversion device 28 Local clock generator 30 Bit processor DP1, DP2, DP3, DP4 Decoding unit DPls1, DPls2, DPls3, DPls4 Decoded optical signal de1, de2, de3, de4 Decoder 40 Circulator 42 Photoelectric conversion circuit 44 Sample hold circuit 46 Bit arithmetic circuit G ′ (i) Fiber grating PS ′ (j) Phase shift unit OE1, OE2, OE3, OE4 Photoelectric conversion unit EL1 Photoelectric conversion signal EPls1 Electric pulse ES1, ES2, ES3, ES4 Electric signal

Claims (4)

Preparing an original optical signal of N bits (where N is an integer of N ≧ 2) and first to Nth codes different from each other;
Encoding processing for encoding the (N−m + 1) th bit (where m is an integer of 1 ≦ m ≦ N) of the original light signal with the mth code is performed for each of the first to Nth bits. The first step of receiving the optical labels arranged on the time axis in a certain cycle and in this order without overlapping the first to Nth diffusion pulses obtained in
A second step of branching the received optical labels into N to generate first to N-th branched optical labels;
Among the first to Nth spread pulses included in the mth branch optical label, the mth spread optical signal is generated by decoding the mth spread pulse positioned in the same order as the number m of the mth branch optical label. A third step of generating first to Nth decoded optical signals including either or both of an autocorrelation optical signal and a cross correlation optical signal by performing the processing to be performed on each of the first to Nth branch optical labels; ,
A process of generating the m-th electrical signal that is a binary electrical signal obtained by photoelectrically converting the m-th decoded optical signal with a threshold value between the intensity of the autocorrelation optical signal and the intensity of the cross-correlation optical signal. A fourth step of generating first to Nth electrical signals by performing each of the Nth decoded optical signals;
A fifth step of reading the binary electrical signal in this order from the first to Nth electrical signals using a local clock signal that is shorter than the cycle of the diffusion pulse and asynchronous.
A method for recognizing an optical label, comprising: recognizing an array of the read binary electric signals as the optical label. In the fourth step, when the m-th decoded optical signal does not include an autocorrelation optical signal, the m-th electrical signal photoelectrically converted to the first voltage from the start point to the end point of the m-th decoded optical signal is And when the mth decoded optical signal includes an autocorrelation optical signal, the first voltage from the start point to the autocorrelation optical signal is the first voltage, and the autocorrelation optical signal to the end point is the Generating the m-th electrical signal photoelectrically converted into a second voltage different from the first voltage,
In the fifth step, the arrangement of the first and second voltages read in this order with the local clock signal one cycle before the end point of the first to Nth electrical signals is expressed as the optical label. The method for recognizing an optical label according to claim 1, wherein: The N-th (N−m + 1) th bit of the original light signal (N− (N−integer of N ≧ 2)) and the first to Nth codes different from each other are used. Here, m is an integer of 1 ≦ m ≦ N), and the first to Nth spread pulses obtained by performing the encoding process for encoding each of the first to Nth bits with the mth code overlap each other. Without receiving, a receiving unit that receives the optical labels arranged on the time axis in a certain periodic interval and in this order;
A branching unit for branching the received optical labels into N to generate first to Nth branched optical labels;
Among the first to Nth spread pulses included in the mth branch optical label, the mth spread optical signal is generated by decoding the mth spread pulse positioned in the same order as the number m of the mth branch optical label. A decoding apparatus that generates first to Nth decoded optical signals including both or one of an autocorrelation optical signal and a cross-correlation optical signal by performing processing for each of the first to Nth branch optical labels; ,
A process of generating the m-th electrical signal that is a binary electrical signal obtained by photoelectrically converting the m-th decoded optical signal with a threshold value between the intensity of the autocorrelation optical signal and the intensity of the cross-correlation optical signal. A photoelectric conversion unit that generates first to Nth electrical signals by performing each of the Nth decoded optical signals;
A local clock generator for generating a local clock signal having a shorter period and asynchronous with respect to the period of the spread pulse;
A bit operation unit that reads out the binary electrical signal in this order from the first to Nth electrical signals using the local clock signal;
An optical label recognition apparatus that recognizes the read-out sequence of the binary electric signals as the optical label. An optical label switch using the optical label recognition device according to claim 3,
A packet branching unit that receives an optical packet composed of the optical label and the payload and separates the optical packet into the optical label and the payload;
The optical label recognition device for recognizing the optical label;
A control signal generator for generating a control signal based on the recognized optical label;
An optical label switch comprising: an optical switch for branching the destination of the payload based on the control signal.

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