JP2005236414A - Light-receiving apparatus and station side apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely convert consecutive light burst signals into electrical signals and to output the electrical signal. <P>SOLUTION: The light receiving apparatus 110 is provided with a light-receiving section 111 for converting the received optical burst signal into the electrical signal and providing an output of the electrical signal; and a reset section 112 for resetting the light receiving section 111, in order to eliminate noise from the electric signal outputted from the light-receiving section 111 according to the detection of the end of the optical burst signal by the light-receiving section 111. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light receiving device and a station side device, and more particularly to a light receiving device and a station side device that receive a burst signal of continuous light.

  Conventionally, in optical networks, optical communication for transmitting and receiving optical signals is performed using an optical medium such as an optical fiber. The light receiving device for receiving the optical signal receives the optical signal transmitted via the communication medium. At this time, the light receiving unit included in the light receiving device converts the received light into an electrical signal.

  Although the prior art regarding the present invention has been described based on general technical information obtained by the applicant, information that should be disclosed as prior art documents before filing within the scope of the applicant's application has been filed. The person does not have.

  However, some of the light receiving devices have a characteristic of outputting noise when a certain time elapses in an extinction state after receiving a burst signal when receiving a burst signal of light. For this reason, if the next light burst signal is received while noise is being output, the next optical signal is detected because the noise is superimposed on the electrical signal converted from the light burst signal. You will not be able to. In particular, when the burst signal of light is received continuously, there is a problem that the influence is large.

  The present invention has been made to solve the above-described problems, and one of the objects of the present invention is to provide a light receiving device capable of reliably converting a continuous burst signal of light into an electric signal and outputting it. Is to provide.

  Another object of the present invention is to provide a station side apparatus capable of reliably detecting a continuous optical burst signal.

  In order to achieve the above-described object, according to one aspect of the present invention, the light receiving device converts the burst signal of the received light into an electrical signal and outputs the electrical signal, and also calculates the burst signal of the light based on the intensity of the received light. Light receiving means for detecting the end, and reset means for resetting the light receiving means in response to the end of the burst signal of light being detected by the light receiving means.

  According to the present invention, when the end of the light burst signal is detected based on the intensity of the received light, the light receiving unit is reset in order to remove noise from the electrical signal output by the light receiving means. For this reason, it is possible to prevent noise from being superimposed on the electrical signal output after the burst signal of the next light is converted. As a result, it is possible to provide a light receiving device capable of reliably converting a continuous burst signal of light into an electrical signal and outputting it.

  Preferably, the reset unit removes noise from the electrical signal output from the light receiving unit.

  According to another aspect of the present invention, the station side device converts the burst signal of the received light into an electrical signal, outputs the electrical signal, detects the start of the burst signal of the light based on the intensity of the received light, and A light receiving device including a light receiving means for outputting a detection signal, a reset means for resetting the light receiving means when a reset signal is given, and a reset to the light receiving device after a predetermined period has elapsed since the burst signal detection signal was received from the light receiving device. Control means for providing a signal.

  According to the present invention, the light receiving means is reset in order to remove noise from the electrical signal output by the light receiving means after a predetermined time has elapsed since the start of the burst signal of the light was detected based on the intensity of the received light. . For this reason, it is possible to prevent noise from being superimposed on the electrical signal output after the burst signal of light received after a predetermined time has elapsed after detecting the start of the burst signal of light. As a result, it is possible to provide a station-side device that can reliably detect a continuous light burst signal.

  According to another aspect of the present invention, the station side device converts the received burst signal of the light into an electrical signal and outputs it, and detects the end of the burst signal of the light based on the intensity of the received light and bursts it. A light receiving device including a light receiving means for outputting a signal detection signal, a reset means for resetting the light receiving means when a reset signal is given, and a reset signal is immediately given to the light receiving device when a burst signal detection signal is received from the light receiving device Control means.

  According to this invention, when the end of the light burst signal is detected based on the intensity of the received light, the light receiving means is reset in order to remove noise from the electrical signal output by the light receiving unit. For this reason, it is possible to prevent noise from being superimposed on the electrical signal output after the burst signal of the next light is converted. As a result, it is possible to provide a station-side device that can reliably detect a continuous light burst signal.

  Preferably, the station side device is connected to a plurality of communication terminals through an optical fiber in a passive double star system, and further includes a communication control means for controlling switching of communication protocols between the plurality of communication terminals and the station side device. The control means further provides a reset signal to the light receiving device on the condition that the communication control means detects that the communication protocol has been switched to the predetermined communication protocol.

  According to the present invention, the station-side device is connected to a plurality of communication terminals via an optical fiber in a passive double star system, and the plurality of communication terminals and the station-side device communicate with each other using a predetermined communication protocol. It is further conditional. For this reason, the light receiving means is reset in order to remove noise only when communication is performed using a predetermined communication protocol in which a burst signal of light is continuously received.

  Preferably, the predetermined communication protocol is a communication protocol used for a station opening process for establishing communication between the station side device and at least one of the plurality of communication terminals.

  According to the present invention, when communication is performed using the communication protocol used for the station opening process for establishing communication between the station side device and at least one of the plurality of communication terminals, a predetermined period from the start of the optical burst signal The light receiving means is reset after elapse of time or immediately after the end of the light burst signal. In the communication protocol for the station opening process, since a common transmission available period is assigned to a plurality of unregistered communication terminals, there is a possibility that an optical burst signal for requesting registration is continuously transmitted. It is possible to reliably detect a continuous burst signal of light in the opening process.

  Preferably, the station side device is connected to a plurality of communication terminals through an optical fiber in a passive double star system, and further includes a communication control means for controlling switching of communication protocols between the plurality of communication terminals and the station side device. The predetermined period is a period defined by the communication protocol switched by the communication control means.

  According to the present invention, the station-side device is connected to a plurality of communication terminals via an optical fiber in a passive double star system, and is defined by a communication protocol used for communication between the plurality of communication terminals and the station-side device. However, the light receiving means is reset in order to remove noise from the electrical signal output by the light receiving means after the light burst signal has started. The transmission protocol that is permitted for each of the plurality of communication terminals is defined by the communication protocol, so that the light receiving unit is reset after the transmission period has elapsed. As a result, it is possible to reliably receive optical burst signals transmitted from a plurality of communication terminals.

  According to still another aspect of the present invention, the station-side apparatus is a station-side apparatus connected to a plurality of communication terminals via an optical fiber in a passive double star system, and the plurality of communication terminals, the station-side apparatus, Light receiving means including a communication control means for controlling the switching of the communication protocol, a light receiving means for converting a burst signal of the received light into an electrical signal, and a reset means for resetting the light receiving means when a reset signal is given. And a control means for giving a reset signal to the light receiving device when a period during which transmission is permitted for each of a plurality of communication terminals is completed, and the period during which transmission is permitted is determined according to a communication protocol switched by the communication control means. The

  According to the present invention, the electrical signal output by the light receiving means when the communication protocol between the plurality of communication terminals and the station side device is switched and the period during which transmission is permitted for each of the plurality of communication terminals is completed according to the switched communication protocol. In order to remove noise from the light receiving means, the light receiving means is reset. For this reason, it is possible to prevent noise from being superimposed on an electric signal obtained by converting a burst signal of light received next. As a result, it is possible to provide a station-side device that can reliably detect a continuous light burst signal.

  Preferably, the reset unit removes noise from the electrical signal output from the light receiving unit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a diagram showing a schematic configuration of a communication system according to the first embodiment of the present invention. Referring to FIG. 1, the communication system in the first embodiment includes a station-side device 100 and a plurality of communication terminals 10, 10A, 10B, 10C, and 10D. Each of the communication terminals 10, 10A to 10D is connected to the computers 11, 11A, 11B, 11C, and 11D through connection lines 24, 24A, 24B, 24C, and 24D. In addition, although the network which connects the five communication terminals 10 and 10A-10D to the station side apparatus 100 is demonstrated to an example here, a communication terminal is not limited to this. Any network may be used as long as one or more communication terminals are connected to one station-side device 100. Here, the communication terminals 10, 10A to 10D and the computers 11, 11A, 11B, 11C, and 11D are directly connected by the connection lines 24, 24A, 24B, 24C, and 24D. , 10A to 10D may be connected to a network such as a local area network (LAN), and computers 11, 11A, 11B, 11C, and 11D may be connected to the network.

  The station-side device 100 and the plurality of communication terminals 10, 10A to 10D are connected by an optical fiber to form a network. Such a network connection form is called a passive double star (PDS) system.

  More specifically, the station side device 100 is connected to one end of the optical fiber 21. The other end of the optical fiber 21 is connected to the optical coupler 23. The optical coupler 23 is connected to the communication terminal 10 by an optical fiber 22. The optical coupler 23 is connected to the communication terminals 10A, 10B, 10C, and 10D through optical fibers 22A, 22B, 22C, and 22D, respectively.

  The optical coupler 23 outputs an optical signal received from one optical fiber 21 to each of the plurality of optical fibers 22 and 22A to 22D. In addition, optical signals received from each of the plurality of optical fibers 22 and 22 </ b> A to 22 </ b> D are output to the optical fiber 21. Therefore, the optical signal output from the station side device 100 is received by the optical coupler 23 via the optical fiber 21, and then output to all the optical fibers 22, 22A to 22D. For this reason, the optical signal output from the station side apparatus 100 is received by all of the communication terminals 10, 10A to 10D.

  On the contrary, since each of the communication terminals 10 and 10A to 10D and the optical coupler 23 are connected by the optical fibers 22 and 22A to 22D, respectively, the optical fiber 22 between the optical coupler 23 and the communication terminals 10 and 10A to 10D. , 22A to 22D are occupied by the communication terminals 10, 10A to 10D, respectively. In other words, the optical signal output from the communication terminal 10 passes only through the optical fiber 22 and does not pass through the optical fibers 22A, 22B, 22C, and 22D.

  Optical signals output from each of the communication terminals 10, 10 </ b> A to 10 </ b> D are collected by the optical coupler 23 and output to the optical fiber 21. For this reason, in the optical fiber 21, all the optical signals output from the communication terminals 10, 10A to 10D are transmitted. In this sense, it can be said that the optical fiber 21 is shared by the communication terminals 10, 10A to 10D. For this reason, in communication between the station-side device 100 and the communication terminals 10, 10 </ b> A to 10 </ b> D, any one of the communication terminals 10, 10 </ b> A to 10 </ b> D can communicate with the station-side device 100. When two or more communication terminals among the plurality of communication terminals 10 and 10A to 10D simultaneously output packets (optical signals) to the station side device 100, the packets collide on the optical fiber 21, and therefore the station side device 100 The packet cannot be received. Note that it is possible to simultaneously transmit and receive light having different wavelengths even with one optical fiber. If the packet transmission from the communication terminals 10, 10 </ b> A to 10 </ b> D to the station-side apparatus 100 is the uplink direction, and the opposite packet transmission is the downlink direction, the wavelength may be different between the uplink direction and the downlink direction. In the present embodiment, it is assumed that packets transmitted in the uplink direction are transmitted using light of the same wavelength.

  When all of the communication terminals 10 and 10A to 10D are connected to the network, the station side device 100 has all of the communication terminals 10 and 10A to 10D connected to avoid packet collision on the optical fiber 21. Registered. Then, the station-side device 100 allocates a period during which each packet can be transmitted to all of the connected communication terminals 10, 10A to 10D, and transmits the allocated period to each of the communication terminals 10, 10A to 10D. ing. For this reason, the communication terminals 10, 10A to 10D transmit packets during the period allocated by the station side device. Therefore, during that period, other communication terminals do not transmit packets, and packets are received by the station side device without colliding on the optical fiber 21.

  However, when a new communication terminal is connected to the station-side apparatus 100, the newly connected communication terminal is not registered in the station-side apparatus 100. In the communication system according to the present embodiment, the process of newly registering a communication terminal in the station side device is called a station opening process. The communication protocol will be described later.

  In the communication system in the present embodiment, the station-side device 100 performs a process of relaying communication between a higher-level network to which the station-side device 100 is connected and the computers 11, 11A to 11D connected to the communication terminals 10, 10A to 10D. Realize. For this reason, communication is performed between the station-side device 100 and the communication terminals 10 and 10A to 10D by transmitting and receiving packets. In order to specify the transmission destination of the packet, MAC (Media Access Control) addresses assigned in advance to the station side device 100 and the communication terminals 10 and 10A to 10D are used. The MAC address is an address given to the MAC layer that is a lower sublayer of the data link layer. Used to specify source and destination in the header of the MAC layer data frame. For the communication using the MAC address, for example, a well-known method defined in IEEE (Institute of Electrical and Electronics Engineers) 802.3ah can be adopted, and detailed description thereof will not be repeated here.

  FIG. 2 is a functional block diagram illustrating an outline of functions of the station side device according to the first embodiment. Referring to FIG. 2, station apparatus 100 includes a transceiver light receiving unit 110 that receives light (hereinafter referred to as “PMD 110”), a transceiver reception control unit 140 that controls PMD 110, and a serial electrical output from PMD 110. A deserializer 120 that converts a signal into a parallel signal, a 10B / 8B conversion (PCS) 130 that converts a 10-bit parallel signal into an 8-bit parallel signal, and a communication control unit 150 that determines a communication protocol are included.

  The light receiving device 110 includes a light receiving unit 111 that converts a strong (1) or weak (0) signal of the received light into a serial electrical signal and outputs the signal to the deserializer 120, and a reset unit 112 for resetting the light receiving unit 111. Including. The light receiving device 110 corresponds to a protocol layer of PMD (Physical Medium Dependent) in IEEE802.3.

  The light receiving unit 111 detects the start and end of the burst signal of the received light, and performs transceiver reception control on a signal detect signal indicating that reception of the burst signal has started or that reception of the burst signal has ended. Output to the unit 140. The light receiving unit 111 outputs noise to the deserializer 120 after a certain time has passed in the extinction state after the reception of the light burst signal. For this reason, the light receiving device 110 includes a reset unit 112 and resets the light receiving unit 111 so as not to generate noise. This reset operation is performed when a reset signal is input from the transceiver reception control unit 140 to the reset unit 112. When the light receiving unit 111 is reset by the reset unit 112 after the reception of the burst signal of light, the light receiving unit 111 does not generate noise even if a certain time elapses in the extinction state. The reset of the light receiving unit 111 by the reset unit 112 may be, for example, activation of a circuit that removes a noise signal output from the light receiving unit 111, or the light receiving unit 111 so that the noise signal is not output from the light receiving unit 111. It may be an operation for returning to the initial state.

  The deserializer 120 converts the serial data transferred from the light receiving device 110 into parallel data. It corresponds to the protocol layer of PMA (Physical Medium Attachement) in IEEE802.3.

  The 10B / 8B converter 130 converts the 10-bit parallel data transferred from the deserializer 120 into 8-bit parallel data that the communication control unit 150 can understand. This corresponds to a protocol layer of PCS (Physical Coding Sublayer) in IEEE802.3.

  The communication control unit 150 corresponds to a protocol layer above these physical layers and has a function of determining a communication protocol.

  When the signal detection signal is input from the light receiving device 110, the transceiver reception control unit 140 outputs a reset signal to the light receiving device 110 at a timing corresponding thereto.

  FIG. 3 is a diagram illustrating an example of a light burst signal input to the light receiving device 110 and an output electric signal. FIG. 3 shows optical burst signals or electrical signals in time series. FIG. 3A is a diagram illustrating a burst signal of light input to the light receiving device 110. Here, an example in which two burst signals are input is shown. In the following description, the burst signal input first is referred to as a first burst signal, and the burst signal input later is referred to as a second burst signal. After the first and second burst signals, there is an extinction state in which the light for a predetermined time is off. Time T1 indicates the time when the first burst signal starts to be received by the light receiving unit 111, and time T1 'indicates the time when the first burst signal has been received by the light receiving unit 111. The burst signal includes a special signal located at the beginning and the end of the burst signal and a data signal located between the two special signals. The configuration of the burst signal is not limited to this, and may be configured by combining other signals. The burst signal may be a combination of strong (1) or weak (0) light.

  FIG. 3B shows an electrical signal output from the light receiving unit when the light receiving unit is not reset. The time (T1 + α) indicates the time when the first burst signal received by the light receiving unit 111 is converted into an electrical signal and the output starts, and the time (T1 ′ + α) indicates the time when the output ends. Time α corresponds to processing time in the light receiving unit 111. Therefore, the light receiving unit 111 outputs an electrical signal obtained by converting the first burst signal from time (T1 + α) to time (T1 ′ + α). FIG. 3B shows the data structure of the special signal and the data signal.

  The light receiving unit 111 outputs an electric signal including a noise signal for a certain period after a predetermined time elapses when the first burst signal is converted into an electric signal and output. FIG. 3B shows a case where the second burst signal is received while the noise signal is being output. When the light receiving unit 111 converts the second burst signal into an electrical signal and outputs it, a noise signal is superimposed on the electrical signal obtained by converting the second burst signal. During this time, the special signal and a part of the data signal included in the second burst signal are erroneously converted by the deserializer 120.

  FIG. 3C shows an electrical signal output from the light receiving unit when the light receiving unit is reset. An electric signal when the light receiving unit 111 is reset by the reset unit 112 after receiving the first burst signal and before receiving the second burst signal is shown. If the light receiving unit 111 is reset after the first burst signal is converted into an electric signal and output, the subsequent electric signal of the noise signal is not output. For this reason, the noise signal is not superimposed on the electrical signal obtained by converting the second burst signal, and is transferred to the deserializer 120.

  As is apparent from this figure, the light receiving unit 111 must be reset after the first burst signal is received and before the second burst signal is received. The timing for resetting the light receiving unit 111 is determined based on the detection of the start of light reception of the burst signal (hereinafter referred to as “on detection type”) and the light reception of the burst signal is terminated. Is determined based on the detection time (hereinafter referred to as “off detection type”). Which of these two types is used may be determined in advance by a user of the station side device 100 and stored in a ROM (read only memory) or the like of the transceiver reception control unit 140, or a dip switch or the like. You may make it switch with a changeover switch. In the case of the off detection type, it may be immediately after the reference time. In the case of the on detection type, it is necessary to predict when the reception of the burst signal ends from the reference time. Depending on the communication protocol, the time length of the burst signal transmitted from the transmission source may be known in advance. The time when the time length of the burst signal becomes the reference may be set as the reset timing. Since an optical burst signal is determined by the frame length transmitted by the burst signal source, it is effective when the frame length is constant. This frame length is determined by the communication protocol. When the frame length is variable, the on-detection type cannot be reset because the frame length cannot be specified. However, even if the frame length is variable, if the maximum frame length is known, the on-detection type reset can be performed if the time required to transmit the maximum frame length is obtained. It becomes possible.

  FIG. 4 is a diagram showing a burst signal of light received by the light receiving unit and timings of starting and ending the light reception. Referring to the figure, in the light receiving unit 111, light reception of the burst signal starts at time T1 and ends at time T1 '. The light receiving level of the burst signal received by the light receiving unit 111 takes a certain time to reach the steady level from the extinction level. In addition, it takes another fixed time from the steady level to the extinction level. The light receiving unit 111 detects the start time of light reception of the burst signal by comparing the light reception level of the burst signal with a predetermined threshold (hereinafter referred to as “on detection”). The light receiving unit 111 detects the end of light reception of the burst signal (hereinafter referred to as “off detection”). That is, when the light receiving level exceeds a threshold value (on detection is detected), the light receiving unit 111 determines that light reception of the burst signal has started and indicates that the light detection of the burst signal has started. (Burst signal detection signal) is output. The light receiving unit 111 determines that the reception of the burst signal has ended when the light reception level falls below the threshold value (detects OFF), and indicates that the reception of the burst signal has ended. Signal detection signal).

  FIG. 5 is a flowchart showing a flow of reset processing executed by the transceiver reception control unit 140 in the present embodiment. FIG. 5A shows a flow of the on detection type reset process. Referring to FIG. 5A, first, it is determined whether or not a signal detect signal is detected (step S01). Here, the detected signal detect signal is a signal detect signal output when the light receiving unit 111 detects ON. If a signal detect signal is detected, the process proceeds to step S02, and if not detected, a standby state is entered (step S01).

  In step S02, a standby state is established for a predetermined time. The predetermined time is longer than the time length of the optical burst signal as described above. Since this predetermined time is a period determined by the communication protocol, it may be stored in advance in a ROM or the like by the communication protocol, or may be input from the communication control unit 150. And when predetermined time passes, it will progress to step S03. In step S03, a reset signal is output to the light receiving unit 111. In the light receiving unit 111 to which the reset signal is input, an electric signal not including noise is output. For this reason, it is possible to prevent noise from being included in the electrical signal obtained by receiving and converting the light burst signal.

  FIG. 5B is a flowchart showing the flow of the off detection type reset process. Referring to FIG. 5B, first, it is determined whether or not a signal detect signal is detected (step S01). Here, the detected signal detect signal is a signal detect signal output when the light receiving unit 111 detects OFF. If a signal detect signal is detected, the process proceeds to step S03, and if not detected, a standby state is entered (step S01).

  In the next step S03, a reset signal is output to the light receiving unit 111. That is, unlike the on detection type reset process, the reset signal is output immediately after the off detection signal detect signal is detected. In the light receiving unit 111 to which the reset signal is input, an electric signal not including noise is output. For this reason, it is possible to prevent noise from being included in the electrical signal obtained by receiving and converting the light burst signal.

  In this way, the off detection type reset process can be applied regardless of the communication protocol because the light receiving unit 111 is reset immediately after the off detection.

  In the station side device 100 in the first embodiment, the light receiving device 110 and the transceiver reception control unit 140 have been described as separate units. However, a transceiver incorporating the transceiver reception control unit 140 may be used.

<Second Embodiment>
FIG. 6 is a functional block diagram illustrating an outline of functions of the station side device according to the second embodiment. Referring to FIG. 6, second station apparatus 100A is different from station apparatus 100 in the first embodiment in that a discovery period signal is output from communication control unit 150. Since other configurations are the same as those of the station-side device 100 in the first embodiment, description thereof will not be repeated here.

  The communication control unit 150 determines a communication protocol. When the communication protocol is a communication protocol used for the opening process, the discovery period signal is output to the transceiver reception control unit 140 while the opening process is being executed. A start signal may be output at the start of the station opening process, and an end signal may be output at the end of the station opening process.

  The transceiver reception control unit 140 switches the type of reset processing between when the discovery period signal input from the communication control unit 150 is input and when it is not input.

  The station opening process is a process for registering an unregistered communication terminal in the station apparatus 100A. FIG. 7 is a diagram showing an opening process procedure executed in the communication system according to the present embodiment. FIG. 7 shows a station opening process procedure executed between the station-side apparatus 100A and the communication terminal 10. First, the station-side device 100A outputs a discovery gate packet that permits periodic transmission of packets to the communication terminal 10, here, transmission of a station opening request packet.

  The discovery gate packet includes the MAC address of the station-side device 100A and information on a time zone during which an opening request packet described later may be transmitted. Further, since the discovery gate packet is output by broadcast, it is received by all of the communication terminals 10, 10A to 10D. When the communication terminal 10 receives the discovery gate packet, the communication terminal 10 outputs a station opening request packet to the station side device 100A in the time zone included in the discovery gate packet.

  The station opening request packet includes the MAC address of the communication terminal 10 and other predetermined information.

  The station-side device 100A extracts the MAC address of the communication terminal 10 in the opening request packet received from the communication terminal 10 and determines whether or not to establish a communication connection with the communication terminal 10.

  When it is determined that the station side device 100A can open the station, a permission packet is transmitted to the communication terminal 10, and when it is determined that the station is not opened, a non-permission packet is transmitted. The permitted packet or the non-permitted packet includes the MAC address of the communication terminal 10 as destination information. Further, the permission packet includes a logical link ID (Logical Link ID) for logically establishing communication between the station-side apparatus 100A and the communication terminal 10. Using this LLID, a logical network connection is established between the communication terminal 10 and the station-side apparatus 100A.

  When receiving a permission packet, the communication terminal 10 outputs a permission confirmation packet to the station side device 100A. At the stage where the station side device 100A receives the permission confirmation packet, the station side device 100A executes processing for establishing communication with the communication terminal 10 and opens the station.

  The station opening process procedure between the station-side apparatus 100A and the communication terminal 10 is generally as described above. The registration process for registering the MAC address of the communication terminal 10 in the station side device 100A and the process for the station side device 100A to establish communication with the communication terminal 10 are executed by this station opening process procedure.

  This station opening processing procedure is one of the communication protocols. In this station opening processing procedure, a station opening request packet transmitted from the communication terminal 10 to the station side device 100A is transmitted as an optical burst signal. The packet length of the station opening request packet is determined in advance. Therefore, since the time from the start to the end of the optical burst signal of the station opening request bucket is known in advance, it may be registered in advance in a storage device such as the RAM of the transceiver reception control unit 140.

  When the communication terminal 10 is registered in the station-side device 100A by this station opening process, a communicable period permitting transmission of packets from the communication terminal 10 is transmitted from the station-side device 100A to the communication terminal 10. . The communication terminal 10 transmits a packet during a period determined by this communicable period. Within this communicable period, the length of the packet is not particularly limited and can be determined on the communication terminal 10 side.

  FIG. 8 is a diagram illustrating a packet received from a communication terminal registered in the station side device. In FIG. 8, when three communication terminals 10, 10A, 10B are registered in the station side device 100A by the above-described opening process, packets ONU # 1, ONU # transmitted from the communication terminals 10, 10A, 10B are shown. 2 shows the temporal relationship between ONU # 3. The station-side device 100A transmits a transmittable period to each of the communication terminals 10, 10A, and 10B. Specifically, the time t1 to t1 ′ is transmitted as the transmittable period to the communication terminal 10, the time t2 to t2 ′ is transmitted as the transmittable period to the communication terminal 10A, and the time is transmitted to the communication terminal 10B. t3 to t3 ′ are transmitted as the transmittable period. From the communication terminals 10, 10A, 10B, packets ONU # 1, ONU # 2, ONU # 3 are transmitted during the designated transmittable period. Therefore, the packets ONU # 1, ONU # 2, ONU # 3 do not overlap in time.

  In the station apparatus 100A, the packet ONU # 1 is received and an electric signal is output from time T1 to time T1 '. Also, the packet ONU # 2 is received and an electrical signal is output from time T2 to time T2 ', and the packet ONU # 3 is received and an electrical signal is output from time T3 to time T3'. There is a case where noise occurs after a predetermined period from time T1 and is superimposed on the electrical signal of the packet ONU # 2.

  FIG. 9 is a flowchart showing the flow of the reset process executed by the station side device 100A in the second embodiment. Here, a case where an off detection type reset process is executed will be described. Referring to FIG. 9, it is first determined whether or not the communication protocol currently used for communication is the communication protocol used in the station opening process (step S11). If true, the process proceeds to step S12. If false, the process proceeds to step S14. The determination in step S11 is determined by whether or not a discovery period signal is input from the communication control unit 150.

  In step S12, it is determined whether or not a signal detect signal is detected. Here, the detected signal detect signal is a signal detect signal output when the light receiving unit 111 detects OFF. If a signal detect signal is detected, the process proceeds to step S13, and if not detected, a standby state is entered (NO in step S12).

  In step S13, a reset signal is output to the light receiving unit 111. In the light receiving unit 111 to which the reset signal is input, an electric signal not including noise is output thereafter. For this reason, it is possible to prevent noise from being included in the electrical signal obtained by receiving and converting the light burst signal.

  On the other hand, if it is determined in step S11 that the communication protocol is not used in the opening process, it is determined whether or not the transmittable period of the communication terminal 10 has ended (step S14). If it is determined that the process has been completed, a reset signal is output to the light receiving unit 111 (step S15). In the light receiving unit 111 to which the reset signal is input, an electric signal not including noise is output thereafter. Thereby, when the communication terminal 10 transmits a packet during the transmittable period, a light burst signal of the packet is received by the light receiving unit 111, but the light receiving unit 111 is reset after the end of the transmittable period. Thereafter, it is possible to prevent noise from being included in the electric signal obtained by receiving and converting the light burst signal.

  In FIG. 9, the reset process for off detection has been described. However, in the station opening process, since the packet length of the station opening request packet is known in advance, the on detection reset process can be used. In this case, the signal detect signal detected in step S12 is a signal detect signal output when the light receiving unit 111 detects ON. Further, a process of waiting for a time exceeding the time necessary for transmitting the optical burst signal of the station opening request packet may be added between step S12 and step S13.

  As described above, the station-side device 100A in the present embodiment outputs a reset signal to the light receiving unit 111 after a predetermined period of time has elapsed since the transceiver reception control unit 140 was turned on by the light receiving unit 111. It is possible to prevent noise from being superimposed on the electrical signal that is converted and output from the burst signal of the light received by the light receiving unit 111 after a predetermined time has elapsed since the unit 111 was turned on. The predetermined time is the time length of the optical burst signal.

  Further, the station-side apparatus 100A outputs a reset signal to the light receiving unit 111 when the transceiver reception control unit 140 is detected to be off by the light receiving unit 111, so that the light receiving unit 111 receives light after the light receiving unit 111 detects off. It is possible to prevent noise from being superimposed on the electrical signal that is converted and output from the optical burst signal.

Furthermore, the reset process is performed when the station-side apparatus 100A is communicating using the communication protocol used for the station opening process. In the station opening process, the station opening request packet from the communication terminal may be continuously transmitted from a plurality of communication terminals during the period designated by the station side device 100A. For this reason, since the reset process is executed during the period for receiving the station opening request packet, it is possible to reliably detect the burst signal of light continuously.
Further, the station-side device 100A transmits a transmittable period from the station-side device 100A to the communication terminal in the communication protocol used for communication after the communication is established between the plurality of communication terminals and the station-side device. This transmittable period is a period defined by the communication protocol. In the station-side apparatus 100A, when the transmittable period ends, the transceiver reception control unit 140 outputs a reset signal to the light receiving unit 111, so that a burst signal of light received thereafter can be reliably detected.

  Furthermore, the station-side device 100A in the second embodiment switches the communication protocol to be used between the station opening process and after the logical link is established. After the logical link is established, the transceiver reception control unit 140 outputs a reset signal to the light receiving unit 111 when the transmission permission period given to each communication terminal is completed according to the communication protocol used after the logical link is established. For this reason, it is possible to prevent noise from being superimposed on the electric signal obtained by converting the burst signal of light received after resetting by the light receiving unit 111.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows schematic structure of the communication system which concerns on the 1st Embodiment of this invention. It is a functional block diagram which shows the outline of the function of the station side apparatus in 1st Embodiment. It is a figure which shows an example of the burst signal of the light input into a light-receiving device, and the electrical signal output. It is a figure which shows the burst signal of the light which a light-receiving part light-receives, and the timing of the start and completion | finish of the light reception. It is a flowchart which shows the flow of the reset process performed in the transceiver reception control part 140 in this Embodiment. It is a functional block diagram which shows the outline of the function of the station side apparatus in 2nd Embodiment. It is a figure which shows the station opening process procedure performed with the communication system in this Embodiment. It is a figure which shows the packet received from the communication terminal registered into the station side apparatus. It is a functional block diagram which shows the outline of the function of the station side apparatus in 2nd Embodiment.

Explanation of symbols

  10, 10A, 10B, 10C, 10D communication terminal, 11, 11A, 11B, 11C, 11D computer, 21, 22, 22A, 22B, 22C, 22D optical fiber, 23 optical coupler, 24, 24A, 24B, 24C, 24D Connection line, 100, 100A station side device, 110 light receiving device, 111 light receiving unit, 112 reset unit, 120 deserializer, 130 10B / 8B conversion, 140 transceiver reception control unit.

Claims (9)

A light receiving means for converting the burst signal of the received light into an electrical signal and outputting it, and detecting the end of the burst signal of the light based on the intensity of the received light;
A light receiving device comprising: a reset unit that resets the light receiving unit when the end of the burst signal of light is detected by the light receiving unit.   The light receiving device according to claim 1, wherein the reset unit removes noise from an electrical signal output from the light receiving unit. A light receiving means for converting the burst signal of the received light into an electrical signal and outputting it, detecting the start of the burst signal of the light based on the intensity of the received light, and outputting a burst signal detection signal;
A light receiving device including a reset means for resetting the light receiving means when a reset signal is given;
A station-side device comprising: control means for providing a reset signal to the light receiving device after a predetermined period has elapsed since the burst signal detection signal was received from the light receiving device. A light receiving means for converting the burst signal of the received light into an electrical signal and outputting it, and detecting the end of the burst signal of the light based on the intensity of the received light and outputting a burst signal detection signal;
A light receiving device including a reset means for resetting the light receiving means when a reset signal is given;
A station-side device comprising control means for providing a reset signal to the light receiving device as soon as a burst signal detection signal is received from the light receiving device. The station side device is connected to a plurality of communication terminals via an optical fiber in a passive double star system,
Further comprising communication control means for controlling switching of communication protocols between the plurality of communication terminals and the station-side device,
5. The station-side device according to claim 3, wherein the control unit gives a reset signal to the light receiving device on the condition that the switching to a predetermined communication protocol is detected by the communication control unit.   The station-side apparatus according to claim 5, wherein the predetermined communication protocol is a communication protocol used for a station opening process for establishing communication between the station-side apparatus and at least one of the plurality of communication terminals. The station side device is connected to a plurality of communication terminals via an optical fiber in a passive double star system,
Further comprising communication control means for controlling switching of communication protocols between the plurality of communication terminals and the station-side device,
The station apparatus according to claim 3, wherein the predetermined period is a period defined by a communication protocol switched by the communication control means. A station-side device connected to a plurality of communication terminals via an optical fiber in a passive double star system,
Communication control means for controlling switching of communication protocols between the plurality of communication terminals and the station side device;
A light receiving device that converts a burst signal of received light into an electrical signal and outputs the light signal; and a light receiving device that includes a reset device that resets the light receiving device when a reset signal is given;
Control means for providing a reset signal to the light receiving device when a period during which transmission is permitted for each of the plurality of communication terminals is completed,
The station-side apparatus, wherein the period during which the transmission is permitted is determined according to a communication protocol switched by the communication control means.   9. The station side device according to claim 3, wherein the reset unit removes noise from an electrical signal output from the light receiving unit.

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