JP2011155564A - Optical receiver and optical transmitter/receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent attenuation of an electric signal owing to the wiring of an optical reception part, in an optical transmitter/receiver corresponding to optical signals having different data rates. <P>SOLUTION: The optical transmitter/receiver is provided with: a photoelectric conversion means for converting first and second optical signals different in data rate into an electric signal and transmitting it; a first CDR(Crock Data Recovery) means for dividing the electric signal output by the photoelectric conversion means into a first electric signal corresponding to the first optical signal and a second electric signal corresponding to the second optical signal, and for reproducing a clock signal from the divided first electric signal, and for adjusting the timing the first electric signal in synchronization with the reproduced clock; and a second CDR means for reproducing the clock based on the second electric signal, and for adjusting the timing of the second electric signal in synchronization with the reproduced clock. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical receiver and an optical transmitter / receiver, and more particularly, to a dual-rate optical receiver and an optical transmitter / receiver that support optical signals having two different data rates.

In recent years, in order to increase the speed of FTTH (Fiber To The Home), the data rate that is currently commercialized is from GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) of the gigabit class, and the data rate is 10 gigabits. Standardization activities and device development to realize a 10G-EPON (10 Gigabit-Ethernet Passive Optical Network) of the highest grade are underway.
In order to upgrade such a system, it is important to maintain compatibility with existing systems. Therefore, a system configuration and a device configuration that operate normally even in a network state where GE-PON and 10G-EPON coexist. It is essential to maintain Therefore, in order to allow coexistence of systems having different data rates, the dual-rate compatibility of optical transmission / reception apparatuses applied to station side apparatuses has been actively studied.

  As a conventional optical transmission / reception apparatus for coexistence of systems having different data rates, for example, an optical transmission / reception apparatus compatible with 1.25 Gbps / 10.3125 Gbps dual rate described in Non-Patent Document 1 is known. FIG. 3 shows a configuration of the optical transmission / reception apparatus 20 compatible with the 1.25 Gbps / 10.3125 Gbps dual rate described in Non-Patent Document 1.

  The optical transceiver 20 includes a 10.3125 Gbps transmission unit (hereinafter referred to as “10G transmission unit”) 211, a 1.25 Gbps transmission unit (hereinafter referred to as “1G transmission unit”) 212, and a dual rate reception unit 213. Optical transceiver module 210 consisting of: 10.3125 Gbps CDR (Clock Data Recovery) section (hereinafter referred to as “10G CDR section”) 220, 1.25 Gbps CDR section (hereinafter referred to as “1G CDR section”) .) 230).

The dual-rate receiving unit 213 described above is expressed as an APD-TIA (Avalanche PhotoDiode-Trance Impedance Amplifier) 213-a that converts an optical signal into a voltage signal and a 10.3125 Gbps limiting amplifier (hereinafter, “10G LIM”). ) 213-b and a 1.25 Gbps limiting amplifier (hereinafter referred to as “1G LIM”) 213-c.
Among the components of the optical transceiver 20 shown in FIG. 3, the 1G transmitter 212, the 1G LIM 213-c and the 1G CDR 230 of the dual rate receiver 213 are optical transceivers used in the conventional GE-PON. The components of the device can be diverted.

  The conventional optical transmission / reception apparatus 20 shown in FIG. 3 receives the 1.25 Gbps / 10.3125 Gbps optical signal transmitted from a plurality of users (transmission sources) by the APD-TIA 213-a and converts it into an electrical signal. By converting and supplying the converted electrical signal to the 10G LIM 213-b and the 1G LIM 213-c, each limiting amplifier can output an electrical signal corresponding to each data rate.

However, the configuration of the conventional optical receiver described in Non-Patent Document 1 has a problem that a limiting amplifier is required for each data rate, leading to an increase in device scale and power consumption.
Further, since it is necessary to separate the signal output of 1.25 Gbps and the signal output of 10.3125 Gbps, the number of required terminals of the optical transceiver module 210 increases, and a low-cost standard size optical transceiver is configured. This makes it difficult to reduce the size and cost of the apparatus.

  In order to solve such a problem, a dual-rate optical transmission / reception apparatus using one limiting amplifier as described in Non-Patent Document 2 has been proposed. FIG. 4 shows a configuration of an optical receiving unit that converts a received optical signal into an electric signal among conventional dual-rate optical transceivers described in Non-Patent Document 2.

The optical receiving unit shown in FIG. 4 includes an optical receiving module 310, a 1G / 10G distribution circuit 313, a 10G CDR 314, and a 1G CDR 315. Here, the optical receiving module 310 includes an APD-TIA 311 and a limiting amplifier (hereinafter referred to as “LIM”) 312. Therefore, an output signal of 1.25 Gbps and an output signal of 10.3125 Gbps can be output from a common terminal, and the number of parts can be reduced, so that the optical transceiver module can be reduced in size and cost.
Among the components of the optical receiver shown in FIG. 4, the CDR of the optical receiver in the optical transceiver used in the conventional GE-PON can be used for the 1G CDR 315.

  The conventional dual rate optical receiver shown in FIG. 4 moves the frequency bands and gains of the APD-TIA 311 and the LIM 312 based on a bit rate determination signal based on an upper layer protocol such as a MAC (Media Access Control) layer. By optimizing the control, the reception sensitivity of the 1.25 Gbps or 10.3125 Gbps signal is optimized according to the reception timing of the 1.25 Gbps or 10.3125 Gbps signal, and the optical signals of different data rates transmitted from the transmission source are respectively set. High sensitivity can be received.

Hirota et al., “Dual-rate OLT Optical Transceiver for 10Gbit / s Burst Signal” 2009 IEICE General Conference, B-10-98, 2009.3. Tajima et al., “Burst Optical Reception Technology Aiming for 1G / 10G Coexistence” 2009 IEICE General Conference, BT-5-3, 2009.3.

However, in the technique described in Non-Patent Document 2, it is necessary to provide a 1G / 10G distribution circuit that distributes an electrical signal of 1.25 Gbps and an electrical signal of 10.3125 Gbps outside the optical reception module. In some cases, the signal line to the CDR circuit corresponding to the electrical signal becomes longer. As described above, since the wiring length from the optical receiving module to the CDR circuit is extended, there is a problem that the signal level of the electrical signal photoelectrically converted by the optical receiving module is attenuated before being input to the CDR circuit. In particular, there has been a problem that communication quality is significantly deteriorated in an electric signal having a high data rate.
Therefore, in order to solve the above-described problems, the present invention provides a small-sized and low-cost device that suppresses the attenuation of the electric signal due to the wiring of the optical receiving unit in the optical receiving device that supports optical signals having different data rates. The purpose is to do.

  In order to achieve the above object, an optical receiver according to the present invention includes a photoelectric conversion unit that converts an optical signal into an electric signal and outputs the first electric signal from the electric signal output by the photoelectric conversion unit. And the second electric signal having a data rate different from that of the first electric signal and outputting the second electric signal, and reproducing the clock from the first electric signal and reproducing the reproduced clock And a first CDR (Crock Data Recovery) means for adjusting the timing of the first electric signal in synchronization with the clock, and a clock is reproduced based on the second electric signal, and the clock is reproduced in synchronization with the reproduced clock. And second CDR means for adjusting the timing of the second electric signal.

  In the present invention, the first CDR means includes a separating means for separating the first and second electric signals from an electric signal output from the photoelectric conversion means, and the first CDR separated by the separating means. CDR means for regenerating a clock from the electric signal of the first, and adjusting the timing of the first electric signal in synchronization with the regenerated clock, and a first terminal for outputting the first electric signal of which the timing has been adjusted And a second terminal for outputting the second electric signal to the second CDR means.

  The first CDR means in the present invention further includes a band limiting means for limiting a frequency band of the second electric signal that is a lower frequency band than the first electric signal separated by the separating means. And the second electric signal whose frequency band is limited by the band limiting means may be output from the second terminal.

In the present invention, the band limiting unit may be composed of at least one of a low-pass filter and an amplifier corresponding to the frequency band of the second electric signal.
Further, the separation means in the present invention may be a switch that distributes the electrical signal to one of two signal paths based on a signal corresponding to a data rate.

The photoelectric conversion means in the present invention may be composed of a photodiode, a preamplifier, and a limiting amplifier.
Further, the first CDR means in the present invention may be configured as one circuit component.

  The optical transmission / reception apparatus according to the present invention is different in data rate from an optical transmission apparatus having a first optical signal transmission unit having a first data rate and a second optical signal transmission unit having a second data rate. In an optical transmission / reception apparatus comprising an optical reception apparatus for receiving an optical signal, the optical reception apparatus is the optical reception apparatus described above, and the photoelectric conversion means, the first optical signal transmission means, and the second optical signal transmission. The means may be modularized in one housing.

According to the present invention, the signal path of the dual-rate electric signal is provided by providing the first CDR means corresponding to the first electric signal with a function of separating the first electric signal and the second electric signal. Since the length can be shortened, the signal attenuation of the electric signal due to the wiring length can be suppressed, and the deterioration of the communication quality can be prevented.
Further, since the required parts and the number of signal output terminals of the optical transceiver module can be reduced, the apparatus can be reduced in size and cost.

It is a block diagram which shows the structure of the optical receiver concerning embodiment of this invention. It is a block diagram which shows the structure of CDR120 for 10G in the optical receiver concerning embodiment of this invention in detail. It is a block diagram which shows the structure of the conventional optical transmitter / receiver corresponding to a dual rate. It is a block diagram which shows the structure of the optical receiver in the conventional optical transmitter / receiver corresponding to a dual rate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The optical transmission / reception apparatus according to the present embodiment is an optical transmission / reception apparatus compatible with dual rates for coexistence of systems having different data rates, and has different bits for CDR (Clock Data Recovery) circuit modules corresponding to high bit rate signals. It has a separation function for separating rate signals. Specifically, a separation circuit that separates signals of different bit rates and a CDR circuit corresponding to a high bit rate signal are configured as one circuit component.
Here, as an optical transmission / reception apparatus according to this embodiment connected to a network in which systems of different data rates are mixed, an optical transmission / reception apparatus connected to a network in which GE-PON and 10G-EPON are mixed will be described as an example. To do.

  As shown in FIG. 1, the optical transmission / reception apparatus according to the present embodiment performs optical signal timing adjustment in 10G-EPON by separating an optical signal from an optical transceiver module 110 that transmits and receives an optical signal and an electric signal having a different data rate. 10G CDR section 120 that executes and outputs an electrical signal by GE-PON, and 1G CDR section 130 that performs timing adjustment of the electrical signal in GE-PON separated and output by 10G CDR section 120. ing.

  An optical transceiver module 110 connected to a communication network receives an APD-TIA (Avalanche PhotoDiode) that receives 10-Gigabit and 1-Gigabit optical signals from 10G-EPON and GE-PON and converts them into electrical signals (voltage signals). -Trance Impedance Amplifier) 111, a limiting amplifier (LIM) 112 that executes the amplitude limitation of this voltage signal with the voltage signal output from APD-TIA 111 as input, and 10G that transmits an optical signal to 10G-EPON The transmission unit 113 includes a 1G transmission unit 114 that transmits an optical signal to the GE-PON. Here, the optical transceiver module 110 has a configuration in which the APD-TIA 111, the LIM 112, the 10G transmission unit 113, and the 1G transmission unit 114 are modularized in one casing.

  The 10G CDR unit 120 connected to the LIM 112 of the optical transceiver module 110 via the input terminal 124 includes a 1G / 10G distribution circuit 121, a 10G CDR circuit core unit 122, a band limiting unit 123, and a first output. The terminal 125 and the second output terminal 126 are configured. Here, the 10G CDR section 120 includes a 1G / 10G distribution circuit 121, a 10G CDR circuit core section 122, a band limiting section 123, a first output terminal 125, and a second output terminal 126. For example, it may be realized as an integrated circuit (IC) integrated on at least one semiconductor substrate.

  Of the components of the 10G CDR unit 120, the 1G / 10G distribution circuit 121 is an electrical signal obtained by photoelectrically converting an optical signal received by the optical transceiver module 110, that is, an electrical signal corresponding to an optical signal by 10G-EPON ( Hereinafter, this is expressed as “first electrical signal”) and an electrical signal in which an electrical signal corresponding to an optical signal generated by GE-PON (hereinafter referred to as “second electrical signal”) is mixed. , Output separately for each data rate.

  The CDR circuit core unit for 10G 122 reproduces a clock from the first electric signal separated and output by the 1G / 10G distribution circuit 121, and adjusts the timing of the first electric signal in synchronization with the reproduced clock. The first electric signal that has been executed and adjusted in timing is output from the second output terminal 125. Details and operation of the configuration of the 10G CDR circuit unit 120 will be described later.

  The band limiting unit 123 limits the frequency band of the second electric signal separated by the 1G / 10G distribution circuit 121, that is, the electric signal corresponding to the optical signal by GE-PON, and the frequency band is limited. 2 electrical signals are output to the 1G CDR unit 130 described later via the second output terminal 126.

  The CDR section 130 for 1G is connected to the second output terminal 126, regenerates a clock from the second electric signal output from the second output terminal 126 and limited in frequency band, and synchronizes with the regenerated clock. Then, the timing adjustment of the second electric signal is executed and output.

  Among the constituent elements of the optical transmission / reception apparatus according to the present embodiment, the 1G CDR unit 130 may use the constituent elements used in the optical transmission / reception apparatus used in the conventional GE-PON as it is. For the optical transceiver module 110, it is possible to use general-purpose parts that have been commercialized.

Next, among the components of the optical transceiver according to the present embodiment, the 10G CDR section 120 that needs to be newly developed will be described in more detail with reference to FIG.
As shown in FIG. 2, the 1G / 10G distribution circuit 121 built in the 10G CDR unit 120 of the optical transceiver according to the present embodiment is a switch having a function of distributing one input signal to two signal paths ( SW) or a selector circuit.

For example, a first electrical signal by 10G-EPON (hereinafter referred to as “10G signal”) and a second electrical signal by GE-PON (hereinafter referred to as “1G signal”) are generated by the SW or selector circuit. The 10G signal and the 1G signal are distributed by distributing the mixed electric signals to two paths of the 1G signal path and the 10G signal path in accordance with the bit rate determination signal from the upper layer protocol such as the MAC layer.
The 10G signal distributed by the 1G / 10G distribution circuit 121 is directly input to the CDR circuit core unit for 10G 122, and clock reproduction and data identification reproduction are executed.
The means for generating the bit rate determination signal has a known content as used in, for example, a dual-rate optical transceiver that is disclosed in Non-Patent Document 2, and will not be described.

  Further, as shown in FIG. 2, the band limiting unit 123 built in the 10G CDR unit 120 is an LPF (low-pass filter) 123-connected to a signal path through which the 1G signal of the 1G / 10G distribution circuit 121 is output. a and the amplifier 123-b.

For example, the LPF 123-a adapted to the frequency band of the 1G signal and the amplifier 123-b having the frequency band characteristics of the 1G signal are configured in the signal path from which the 1G signal of the 1G / 10G distribution circuit 121 is output. The frequency band characteristics of the 1G signal output from the 1G / 10G distribution circuit 121 are limited so that the reception sensitivity of the 1G signal is optimized.
Since the LPF 123-a and the amplifier 123-b described above have band characteristics that optimize the reception sensitivity of the 1G signal, the characteristics of the LIM 112 of the optical transceiver module 110 are optimal for increasing the sensitivity of the 10G signal. Even in such a case, it is possible to improve the reception sensitivity of the 1G signal.

  The 1G signal that has passed through the LPF 123-a and the amplifier 123-b and whose frequency band is limited is directly input to the 1G CDR unit 130 via the second output terminal 126.

Next, a case where all the functions of the CDR section 120 for 10G shown in FIG. 2 are mounted on one integrated circuit (IC) will be described as an example.
As described above, since the function of the 1G / 10G distribution circuit 121 can be realized by a switch or a selector circuit, a switch or a selector circuit whose circuit scale is much smaller than that of a CDR circuit may be mounted. Therefore, a 10G CDR unit 120 incorporating a 1G / 10G distribution circuit 121 is realized on a semiconductor substrate as a single integrated circuit (IC) with a circuit scale almost equivalent to that of a CDR circuit not mounted with a 1G / 10G distribution circuit. can do.

On the other hand, the band limiting unit 123 configured on the signal path of the 1G signal can also be mounted on the 1G CDR unit 130. In this case, in order to implement the band limiting unit 123 in the 1G CDR unit 130, it is necessary to customize the CDR unit of the optical transceiver used in the conventional GE-PON, that is, for the 1G CDR unit 130 Need to be customized separately.
However, by mounting the band limiting unit 123 on the 10G CDR unit 120 as in the optical transmission / reception device according to the present embodiment, the optical transmission / reception device used in the existing GE-PON as the 1G CDR unit 130 is provided. CDR portions can be used.

  As described above, according to the optical transmission / reception apparatus according to the present embodiment, the 1G / 10G distribution circuit 121 and the band limiting unit 123 are incorporated in the 10G CDR unit 120, whereby the first and second The signal path length of the electrical signal can be made shorter than that of the conventional optical transceiver, and the attenuation of the electrical signal due to the extension of the line length can be suppressed.

  In particular, when all the functions of the CDR section 120 for 10G are realized by being mounted on one integrated circuit (IC), the first electrical signal (10G signal) separated by the 1G / 10G distribution circuit 121 is converted to 10G. Since the signal path length of the 10G signal can be shortened because the signal can be directly input to the CDR circuit core unit 122, the attenuation of the 10G signal due to the wiring length can be suppressed, and deterioration of communication quality can be prevented.

  Further, by optimizing the reception sensitivity of the 10G signal and 1G signal by the 1G / 10G distribution circuit 121 and the band limiting unit 123 built in the CDR unit 120 for 10G, more accurate clock reproduction and data identification reproduction can be achieved. Therefore, the frequency band and gain switching control according to the reception timing of the 10G signal and the 1G signal for the LIM 112 and the APD-TIA 111 of the optical transceiver module 110 can be omitted.

Further, according to the optical transmission / reception apparatus according to the present embodiment, the 1G signal and the 10G signal output from the LIM 112 can be processed by the CDR unit 120 for 10G, so that the required components and signal output of the optical transceiver module 110 are processed. The number of terminals can be reduced.
Furthermore, if only the component corresponding to the 10G CDR unit 120 is newly modularized among the components of the optical transceiver according to the present embodiment, the signal length of the 10G signal is shortened. As for the above-described components, it is possible to divert the components of the optical transceiver used in the existing GE-PON and the existing components for 10G signals.
Accordingly, it is possible to select relatively inexpensive parts and reduce the number of control terminals necessary for the photoelectric conversion means, and thus it is possible to reduce the size and cost of the apparatus. .

  Further, since the 1G / 10G distribution circuit 121 is realized by a switch or a selector circuit, a high data rate signal and a low data rate signal can be completely separated. Therefore, it is possible to improve resistance to noise such as crosstalk in the entire circuit of the optical transceiver.

  In FIG. 2, the band limiting unit 123 configured in the path of the 1G signal in the 10G CDR unit 120 is illustrated as having an LPF 123-a and an amplifier 123-b. One of the configurations may be adopted.

  INDUSTRIAL APPLICABILITY The present invention can be used for an optical transmission / reception apparatus applied to a station side apparatus in an FTTH (Fiber To The Home) system.

  DESCRIPTION OF SYMBOLS 20 ... Optical transmission / reception apparatus, 110, 210 ... Optical transceiver module, 111, 213-a, 311 ... APD-TIA (Avalance PhotoDiode-Trance Impedance Amplifire), 112, 312 ... LIM (Limiting amplifier), 113, 211 ... 10G Transmission unit, 114, 212 ... 1G transmission unit, 120, 220, 314 ... 10G CDR unit, 121,313 ... 1G / 10G distribution circuit, 122 ... 10G CDR circuit core unit, 123 ... band limiting unit, 123-a ... LPF, 123-b ... Amplifier, 124 ... Input terminal, 125 ... First output terminal, 126 ... Second output terminal, 130, 230, 315 ... 1G CDR unit, 213 ... Dual rate receiving unit, 213- b ... LIM for 10G, 213-c ... LIM for 1G, 310 ... Optical receiver module.

Claims (8)

Photoelectric conversion means for converting an optical signal into an electrical signal and outputting the electrical signal;
While separating the first electric signal and the second electric signal having a data rate different from the first electric signal from the electric signal output by the photoelectric conversion means, the second electric signal is output. First CDR (Crock Data Recovery) means for regenerating a clock from the first electric signal and adjusting the timing of the first electric signal in synchronization with the regenerated clock;
An optical receiver comprising: a second CDR unit that regenerates a clock based on the second electric signal and adjusts the timing of the second electric signal in synchronization with the regenerated clock. The optical receiver according to claim 1,
The first CDR means includes:
Separating means for separating the first and second electrical signals from the electrical signal output from the photoelectric conversion means;
CDR means for regenerating a clock from the first electrical signal separated by the separation means and adjusting the timing of the first electrical signal in synchronization with the regenerated clock;
A first terminal for outputting the first electric signal, the timing of which is adjusted;
And a second terminal for outputting the second electric signal to the second CDR means. The optical receiver according to claim 2,
The first CDR means further comprises:
Band limiting means for limiting the frequency band of the second electric signal that is a lower frequency band than the first electric signal separated by the separating means;
The optical receiving apparatus according to claim 1, wherein the second electric signal whose frequency band is limited by the band limiting unit is output from the second terminal. The optical receiver according to claim 3.
The optical band receiving means comprises at least one of a low-pass filter and an amplifier corresponding to the frequency band of the second electric signal. The optical receiver according to any one of claims 2 to 4,
The optical receiving apparatus, wherein the separating means is a switch that distributes the electric signal to one of two signal paths based on a signal corresponding to a data rate. The optical receiver according to any one of claims 1 to 5,
The photoelectric conversion device comprises a photodiode, a preamplifier, and a limiting amplifier. The optical receiver according to any one of claims 1 to 6,
The optical receiver according to claim 1, wherein the first CDR means is configured as one circuit component. An optical transmission device having a first optical signal transmission unit having a first data rate and a second optical signal transmission unit having a second data rate, and an optical reception device receiving optical signals having different data rates. In an optical transceiver,
The optical receiver is the optical receiver according to any one of claims 1 to 7,
The optical transmission / reception apparatus, wherein the photoelectric conversion unit, the first optical signal transmission unit, and the second optical signal transmission unit are modularized in one casing.

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