JP2012249170A - Optical packet transmitter/receiver and optical packet receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To receive an optical packet appropriately even when the level difference is large between the optical packets.SOLUTION: An optical packet receiver 14 receiving an optical packet to which the light level information is added comprises: an optical switch unit 21 which outputs an optical packet to any one of first through fourth output ports OP1-OP4 depending on the light level information added to a header of an input optical packet; first through fourth variable optical attenuators 23a-23d provided in the first through fourth output ports OP1-OP4 of the optical switch unit 21; an optical coupler 28 provided in the subsequent stage thereof; and an optical receiver 30 which receives an optical packet output from the optical coupler 28. Attenuation of the first through fourth variable optical attenuators 23a-23d is set, respectively, so that the peak power of the optical packet thus output falls within a predetermined receivable range R.

Description

  The present invention relates to an optical packet switching system that enables packet switching in units of optical packets by switching optical switches according to path information given to optical packet signals.

  2. Description of the Related Art In an optical transmission system using wavelength division multiplexing (WDM), a technology for performing path switching in units of wavelengths by using a wavelength selective switch (WSS) or the like has been put into practical use. As the next technology, the unit for switching is made into a fine unit such as an IP packet (10 GEther (10 Gigabit Ethernet (registered trademark)) signal, for example) one by one, and each is converted into a format of an optical packet, which is ultra-high speed. An optical packet switching method in which a route is switched by using an optical switch has been studied (see, for example, Patent Document 1).

  As long as there is no data in the IP packet, no significant information is transferred, and the bandwidth is wasted by that amount, but if the optical packet switching method is realized, the time zone in which no data exists will be transferred to another packet. Can be occupied. Therefore, the optical packet switching method has the potential to dramatically increase the bandwidth utilization efficiency of the transmission path, and is considered promising as a future technology.

JP 2008-235986 A

  In the optical packet switching method, since the packet length changes for each optical packet, there are a time zone in which an optical signal exists and a time zone in which no optical signal exists. Here, “packet density” is defined as an index representing the ratio of optical signals. Packet density is defined as packet length / packet interval.

  In an optical packet switching system, when an optical packet is output by an optical packet transmission device, the peak power of the optical packet output varies according to the packet density. Therefore, the optical receiver of the optical packet switching system is required to receive optical packets having various peak powers. As used herein, “peak power” means the optical power level when the optical signal is “1”.

  FIG. 1 shows an example of an optical packet signal input to the optical receiver. FIG. 1 shows that an optical packet # 2 having a small peak power is input after an optical packet # 1 having a large peak power. An interval between adjacent optical packets # 1 and # 2 is referred to as an “optical packet interval”. The peak power difference between adjacent optical packets # 1 and # 2 is referred to as “inter-optical packet level difference”. In general, when the optical packet interval is short and the level difference between the optical packets is large, it is difficult for the optical receiver to perform an appropriate reception process. This point will be described below.

  FIG. 2 shows an example of the configuration of the optical receiver. As shown in FIG. 2, the optical receiver 100 includes a PIN-PD 102, a preamplifier 104, a coupling capacitor 105, a limiter amplifier 106, a G-VCO 108, a bandpass filter 110, a D flip-flop 112, An amplifier 114 and a capacitor 116 are provided.

  The optical packet signal input to the optical receiver 100 is converted into an electrical signal by the PIN-PD 102 and then amplified by the preamplifier 104. The preamplifier 104 is a differential output preamplifier. The packet signal output from the preamplifier 104 is amplified by the limiter amplifier 106 via the coupling capacitor 105. The packet signal output from the limiter amplifier 106 is input to the G-VCO 108 and the D flip-flop 112.

  A G-VCO (Gated Voltage-Controlled-Oscillator) 108 adjusts the phase of the oscillated clock to the phase of the input packet signal and outputs it to the bandpass filter 110. The clock output from the band pass filter 110 is amplified by the amplifier 114 and then output as differential clocks A and B via the capacitor 116. The G-VCO 108, the bandpass filter 110, the amplifier 114, and the capacitor 116 constitute a timing extraction circuit.

  A packet signal (data) from the limiter amplifier 106 and a clock from the amplifier 114 are input to the D flip-flop 112. The D flip-flop 112 discriminates and reproduces the packet signal and then outputs it as data A and B.

  Here, as shown in FIG. 1, when an optical packet # 2 having a low peak power is input to the optical receiver 100 immediately after the optical packet # 1 having a high peak power, the charge of the optical packet # 1 is released from the capacitor 116. Since it takes time to complete, it is difficult to extract the clock from the optical packet # 2. As a result, the phase of the data and clock input to the D flip-flop 112 becomes indefinite, and there is a possibility that the optical packet # 2 cannot be identified and reproduced.

  FIG. 3 shows a relationship between an optical packet interval at which an optical packet with a low peak power cannot be received and an optical packet level difference when an optical packet with a low peak power is input after an optical packet with a high peak power. . For example, when the optical packet interval is 25 ns and the level difference between the optical packets is 3 dB or more, the subsequent optical packet with a small peak power cannot be received by the optical receiver.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique capable of appropriately receiving an optical packet even when the level difference between optical packets is large.

  In order to solve the above problems, an optical packet transmitting / receiving apparatus according to an aspect of the present invention includes an optical packet transmitting apparatus that transmits an optical packet to which optical level information is added, and an optical packet receiving apparatus that receives the optical packet. . The optical packet receiving apparatus includes: an optical switch unit that outputs the optical packet to one of a plurality of output ports according to optical level information added to a header of the input optical packet; and each output port of the optical switch unit A plurality of optical attenuators provided for each, a plurality of optical attenuators, each of which is set so that the peak power of the output optical packet is within a predetermined receivable range, and a plurality of optical attenuators An optical coupler provided at the subsequent stage of the optical attenuator and an optical receiver for receiving an optical packet output from the optical coupler.

  The optical switch unit may include a table in which the optical level of the optical packet is associated with the output port of the optical packet, and may determine the output port of the input optical packet with reference to the table.

  The optical attenuator is a variable optical attenuator, and the optical packet receiver receives an optical level monitor that detects the peak power of the optical packet output from each variable optical attenuator, and the peak power information detected by the optical level monitor. And an attenuation amount control unit for controlling the attenuation amount of each variable optical attenuator so that the peak power of the optical packet output from each variable optical attenuator falls within the receivable range.

  The optical packet receiver may further include a BER detector that detects a bit error rate of the optical packet received by the optical receiver. The attenuation amount control unit may control the attenuation amount of the variable optical attenuator based on the bit error rate information detected by the BER detection unit in addition to the peak power information.

  Another aspect of the present invention is an optical packet receiver. The apparatus is an optical packet receiving apparatus that receives an optical packet to which optical level information is added. The optical packet is transmitted to a plurality of output ports according to the optical level information added to the header of the input optical packet. And a plurality of optical attenuators provided for each output port of the optical switch unit so that the peak power of the output optical packet is within a predetermined receivable range. A plurality of optical attenuators in which the respective attenuation amounts are set, an optical coupler provided at a subsequent stage of the plurality of optical attenuators, and an optical receiver that receives an optical packet output from the optical coupler.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between an apparatus, a method, a system, a program, a recording medium storing the program, and the like are also effective as an aspect of the present invention.

  According to the present invention, an optical packet can be appropriately received even when the level difference between optical packets is large.

It is a figure which shows an example of the optical packet signal input into an optical receiver. It is a figure which shows an example of a structure of an optical receiver. It is a figure which shows the relationship between the optical packet space | interval which cannot receive an optical packet with small peak power, and the level difference between optical packets. It is a figure which shows the optical packet transmission / reception apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the structure of an optical packet transmitter. It is a figure which shows an example of the format of an optical packet. It is a figure for demonstrating the structure of an optical packet receiver. It is a figure which shows an example of the table which matched the optical level and the output port. It is a figure for demonstrating control of an attenuator control part.

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

  FIG. 4 shows an optical packet transmitting / receiving apparatus 10 according to the embodiment of the present invention. As shown in FIG. 4, first to fourth optical packet transmitters 12a to 12d that transmit optical packets, and an optical packet receiver 14 that receives optical packets from the first to fourth optical packet transmitters 12a to 12d. With.

  FIG. 5 is a diagram for explaining the configuration of the optical packet transmitter. As illustrated in FIG. 5, the optical packet transmission device 12 adds a header to an input client signal to generate a packet of an electrical signal, and optically transmits the packet generated by the packet generation unit 16. And an electrical / optical converter 18 that converts the packet into an output.

  The packet generation unit 16 includes a packet length information addition unit 20 that adds packet length information to the packet header, and an optical level information addition unit 22 that adds optical level information to the packet header. The optical level information added by the optical level information adding unit 22 is a peak power when an electric signal packet is converted into an optical packet by the electric / optical converting unit 18. As described above, the peak power of the optical packet varies depending on the packet density. Since the packet generation unit 16 knows the packet density, the peak power of the optical packet after the electrical / optical conversion can be estimated at the electrical signal stage. For example, the optical level information adding unit 22 classifies the optical level of the optical packet into four levels of “extra large”, “large”, “medium”, and “small”, and adds the information to the header.

  FIG. 6 shows an example of the format of an optical packet. As shown in FIG. 6, the optical packet is composed of data as a user area and a header provided before the data. The header has optical level information and packet length information. Although not shown in FIG. 6, the header may include destination information for optical packet exchange, transmission source information of the optical packet, and the like.

  FIG. 7 is a diagram for explaining the configuration of the optical packet receiving apparatus. As shown in FIG. 7, the optical packet receiver 14 includes an optical switch unit 21, first to fourth variable optical attenuators 23a to 23d, first to fourth optical branching couplers 24a to 24d, Fourth optical level monitors 26a to 26d, an optical coupler 28, an optical receiver 30, a BER detector 32, and an attenuator controller 34 are provided.

  The optical switch unit 21 includes four input ports (first to fourth input ports IP1 to IP4), four output ports (first to fourth output ports OP1 to OP4), and an analysis unit 36. In the present embodiment, an optical packet from the first optical packet transmitter 12a is input to the first input port IP1, an optical packet from the second optical packet transmitter 12b is input to the second input port IP2, and the first An optical packet from the third optical packet transmitter 12c is input to the third input port IP3, and an optical packet from the fourth optical packet transmitter 12d is input to the fourth input port IP4.

  The optical switch unit 21 sends the optical packet to the first to fourth output ports OP1 to OP4 according to the optical level information added to the header of the optical packet input to the first to fourth input ports IP1 to IP4. Output to either.

  The analysis unit 36 analyzes the header of the optical packet input to the first to fourth input ports IP1 to IP4, and extracts optical level information and packet length information. The analysis unit 36 includes a table in which the optical level of the optical packet is associated with the output port of the optical packet, and determines the output port of the input optical packet with reference to the table. FIG. 8 shows an example of a table in which light levels are associated with output ports. As shown in FIG. 8, an optical packet having an optical level “extra large” is output to the first output port OP1, an optical packet having an optical level “high” is output to the second output port OP2, and the optical level is “medium”. Is output to the third output port OP3, and the optical packet having the optical level “low” is output to the first output port OP4. The packet length information is used by the optical switch unit 21 to determine the end of the optical packet.

  Subsequent stages of the first to fourth output ports OP1 to OP4 are provided with first to fourth variable optical attenuators 23a to 23d, respectively, for attenuating input optical packets. The attenuation amount of each of the first to fourth variable optical attenuators 23 a to 23 d is controlled by the attenuator control unit 34.

  First to fourth optical branching couplers 24a to 24d are provided at the subsequent stages of the first to fourth variable optical attenuators 23a to 23d, respectively. Each of the first to fourth optical branching couplers 24 a to 24 d branches the input optical packet, outputs one to the first to fourth optical level monitors 26 a to 26 d, and outputs the other to the optical coupler 28.

  Each of the first to fourth optical level monitors 26a to 26d detects the peak power of one input optical packet. The detected peak power information is input to the attenuator control unit 34.

  The optical coupler 28 is provided in the subsequent stage of the first to fourth optical branching couplers 24a to 24d, and multiplexes the other input optical packet.

  The optical receiver 30 receives the optical packet output from the optical coupler 28 and performs predetermined reception processing such as equalization amplification (Reshaping), retiming (Retiming), and identification regeneration (Regenerating). The configuration of the optical receiver 30 may be the same as that of the optical receiver 100 shown in FIG. 2, for example.

  The BER detector 32 detects the bit error rate of each optical packet received by the optical receiver 30. The bit error rate information of each optical packet detected by the BER detection unit 32 is input to the attenuator control unit 34.

  Next, the operation of the optical packet transmitting / receiving apparatus 10 according to the present embodiment will be described with reference to FIG. Here, the optical packet # 1 output from the third optical packet transmitter 12c is input to the third input port IP3 of the optical switch unit 21, and the optical packet # 2 output from the fourth optical packet transmitter 12d is optical. An optical packet # 3 input to the third input port IP4 of the switch unit 21 and output from the first optical packet transmitter 12a is input to the first input port IP1 of the optical switch unit 21, and the second optical packet transmitter 12b. Consider a case where the optical packet # 4 output from is input to the second input port IP2 of the optical switch unit 21. Optical packets are input to the optical switch unit 21 in the order of optical packets # 1, # 2, # 3, and # 4. The optical level of the optical packet # 1 is “extra large”, the optical level of the optical packet # 2 is “medium”, the optical level of the optical packet # 3 is “high”, and the optical level of the optical packet # 4 The level is “Small”. When optical packets # 1 to # 4 are multiplexed by an optical coupler, it is assumed that optical packet # 2 immediately after optical packet # 1 cannot be received by a normal optical receiver because the level difference between optical packets is large. Further, it is assumed that the optical packet # 4 immediately after the optical packet # 3 cannot be received by a normal optical receiver because the level difference between the optical packets is large.

  The analysis unit 36 of the optical switch unit 21 analyzes the header of each input optical packet # 1 to # 4, and extracts optical level information and packet length information. Then, the output port of each packet is selected with reference to the table shown in FIG. Specifically, the optical packet # 1 input to the third input port IP3 is output from the first output port OP1 because the optical level information is “extra large”. The optical packet # 2 input to the fourth input port IP4 is output from the third output port OP3 because the optical level information is “medium”. The optical packet # 3 input to the first input port IP1 is output from the second output port OP2 because the optical level information is “large”. The optical packet # 4 input to the second input port IP2 is output from the fourth output port OP4 because the optical level information is “low”.

  The optical packets output from the first to fourth output ports OP1 to OP4 are input to the first to fourth variable optical attenuators 23a to 23d. Here, in the present embodiment, the attenuator control unit 34 makes the peak power of the optical packet output from each of the first to fourth variable optical attenuators 23a to 23d fall within a predetermined receivable range R. The amount of attenuation of each of the first to fourth variable optical attenuators 23a to 23d is controlled. The receivable range R is a range in which the optical receiver 30 in the subsequent stage can appropriately receive within the range.

  FIG. 9 is a diagram for explaining the control of the attenuator control unit. Immediately after the apparatus is activated, the peak power of the input optical packet may not be accurately known. In such a case, the attenuator control unit 34 sets the attenuation amount according to the following procedure. Here, the first variable attenuator 23a will be described as an example.

  (1) First, the first optical packet is passed through the first variable attenuator 23a without being attenuated.

  (2) The peak power of the first optical packet is detected by the first optical level monitor 26a.

  (3) The attenuator control unit 34 controls the attenuation amount of the first variable attenuator 23a based on the detected peak power information of the first optical packet. Specifically, it is determined whether or not the peak power of the first optical packet is within the receivable range R. If it is not within the receivable range R, the peak power of the first optical packet can be received. The amount of attenuation necessary to be within the range R is calculated. Then, the first variable attenuator 23a is controlled to be the attenuation amount. On the other hand, if it is within the receivable range R, there is no problem with the attenuation amount as it is (that is, no attenuation), so the attenuation amount is maintained.

  (4) The next input optical packet is attenuated by the attenuation amount set by the first variable attenuator 23a. Since the optical packet output from the first output port OP1 by the optical switch unit 21 is limited to the optical level of “extra large”, the peak power of the next optical packet is set within the receivable range R. Can do. Monitoring of the peak power by the first optical level monitor 26a is always performed, and when the peak power exceeds the receivable range R, the attenuation amount is set again.

  The above attenuation control is performed in the same manner for the second to fourth variable optical attenuators 23b to 23d. As a result, the peak powers of the optical packets # 1 to # 4 output from the first to fourth variable optical attenuators 23a to 23d are within the receivable range R.

  Returning to FIG. 7, the optical packets # 1 to # 4 output from the first to fourth variable optical attenuators 23a to 23d are input to the optical coupler 28 via the first to fourth optical level monitors 26a to 26d. The The optical coupler 28 multiplexes the optical packets # 1 to # 4 and outputs them to the optical receiver 30. The optical packets # 1 to # 4 input to the optical receiver 30 have a peak power within the receivable range R, and the level difference between the optical packets is reduced. # 1 to # 4 can be received appropriately.

  Since the receivable range R varies depending on the performance of the optical receiver 30, it may be set as appropriate through experiments and simulations.

  The attenuator control unit 34 may control the attenuation amounts of the first to fourth variable optical attenuators 23 a to 23 d based on the bit error rate information detected by the BER detection unit 32. Specifically, the attenuator control unit 34 feedback-controls the attenuation amounts of the first to fourth variable optical attenuators 23a to 23d so that the bit error rate decreases. Thereby, the attenuation amount of the 1st-4th variable optical attenuator 23a-23d can be set to an appropriate value, and a favorable receiving state can be maintained.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications are possible depending on the combination of each component and each processing process, and such modifications are within the scope of the present invention. is there.

  For example, when the peak power of the optical packet output from each output port of the optical switch unit 21 is known in advance and hardly fluctuates, the attenuation amounts of the first to fourth variable optical attenuators 23a to 23d are It may be fixed. Further, in this case, the variable optical attenuator is not required, and an attenuator having a fixed attenuation may be used.

  DESCRIPTION OF SYMBOLS 10 Optical packet transmitter / receiver, 12 Optical packet transmitter, 14 Optical packet receiver, 16 Packet generator, 18 Electrical / optical converter, 20 Packet length information addition part, 21 Optical switch part, 22 Optical level information addition part, 28 Optical coupler, 30 optical receiver, 32 BER detector, 34 attenuator controller, 36 analyzer.

Claims (8)

An optical packet transmitter for transmitting an optical packet to which optical level information is added;
An optical packet transmission / reception device comprising an optical packet reception device for receiving an optical packet,
The optical packet receiver is
An optical switch unit that outputs the optical packet to one of a plurality of output ports according to the optical level information added to the header of the input optical packet;
A plurality of optical attenuators provided for each output port of the optical switch unit, wherein a plurality of attenuations are set such that the peak power of the output optical packet is within a predetermined receivable range. With an optical attenuator
An optical coupler provided at a subsequent stage of the plurality of optical attenuators;
An optical receiver for receiving an optical packet output from the optical coupler;
An optical packet transmitting / receiving apparatus comprising:   The optical switch unit includes a table in which an optical level of an optical packet is associated with an output port of the optical packet, and determines an output port of the optical packet with reference to the table. The optical packet transmitting / receiving apparatus as described. The optical attenuator is a variable optical attenuator;
The optical packet receiver is
An optical level monitor that detects the peak power of the optical packet output from each variable optical attenuator;
Based on the peak power information detected by the optical level monitor, the attenuation amount of each variable optical attenuator is controlled so that the peak power of the optical packet output from each variable optical attenuator falls within the receivable range. An attenuation control unit;
The optical packet transmitting / receiving apparatus according to claim 1, further comprising: The optical packet receiver is
A BER detector for detecting a bit error rate of an optical packet received by the optical receiver;
The said attenuation amount control part controls the attenuation amount of the said variable optical attenuator based on the bit error rate information detected by the said BER detection part in addition to peak power information. Optical packet transmitter / receiver. An optical packet receiving device that receives an optical packet to which optical level information is added,
An optical switch unit that outputs the optical packet to one of a plurality of output ports according to the optical level information added to the header of the input optical packet;
A plurality of optical attenuators provided for each output port of the optical switch unit, wherein a plurality of attenuations are set such that the peak power of the output optical packet is within a predetermined receivable range. With an optical attenuator
An optical coupler provided at a subsequent stage of the plurality of optical attenuators;
An optical receiver for receiving an optical packet output from the optical coupler;
An optical packet receiving apparatus comprising:   The optical switch unit includes a table in which an optical level of an optical packet is associated with an output port of the optical packet, and performs route switching of the input optical packet with reference to the table. Item 6. The optical packet receiver according to Item 5. The optical attenuator is a variable optical attenuator;
An optical level monitor that detects the peak power of the optical packet output from each variable optical attenuator;
Based on the peak power information detected by the optical level monitor, the attenuation amount of each variable optical attenuator is controlled so that the peak power of the optical packet output from each variable optical attenuator falls within the receivable range. An attenuation control unit;
The optical packet receiver according to claim 5, comprising: A BER detector for detecting a bit error rate of an optical packet received by the optical receiver;
The said attenuation amount control part controls the attenuation amount of the said variable optical attenuator based on the bit error rate information detected by the said BER detection part in addition to peak power information. Optical packet receiver.

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