Optical receiving device, station side device, PON system, preamplifier, optical receiving method and integrator output reversal suppression method

Abstract

An optical receiving device for receiving a burst optical signal comprises: a light receiving element for receiving an optical signal; an amplifier for receiving and amplifying a current based on an input current from the light receiving element; a DC adjustment circuit connected to an input electrical route from the light receiving element to the amplifier for removing an offset current contained in the input current; an AC adjustment circuit connected to the input electrical route through which a portion of the input current flows; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit comprising: an integrator for integrating the output of the amplifier and outputting it to two electrical routes of a positive phase and a negative phase; and a reverse suppression circuit for operating in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

Description

Technical Field

[0001] The present disclosure relates to an optical receiving device, a station side device, a PON system, a preamplifier, an optical receiving method, and an output reversal suppression method of an integrator.

[0002] This application claims the priority based on Japanese Application No. 2019-110446 filed on June 13, 2019, and cites all the contents described in the Japanese Application. Background Art

[0003] In the optical receiving device for optical reception, the burst optical signal received by the photodiode is output as a differential signal via a preamplifier (TIA: Transimpedance Amplifier) ​​(for example, refer to Patent Document 1). The station side device of the PON (Passive Optical Network) system is connected to multiple terminal devices (residential side devices) via optical fibers. Therefore, the distance from the terminal device to the station side device is uneven, and the intensity of the optical signal reaching the optical receiving device mounted on the station side device varies greatly for each terminal device.

[0004] Therefore, an adjustment circuit is provided to release (or extract) a portion of the current converted by the photodiode. When the intensity of the light signal is high, a portion of the current is released, and when the intensity of the light signal is weak, the release function is stopped (for example, refer to Patent Documents 2 and 3). It is considered that in order to stop the release, a negative offset voltage can be applied to the reference voltage so that it is lower than the output of the amplifier stage. When a portion of the current is released, closed-loop control is achieved, and when the release function is stopped, open-loop control is achieved.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-250137

[0008] Patent Document 2: Japanese Patent Application Publication No. 2012-60436

[0009] Patent Document 3: International Publication WO2016 / 035374A1 Summary of the invention

[0010] Technical solutions to solve problems

[0011] The present disclosure includes the following inventions. However, the present invention is defined by the claims.

[0012] (Light receiving device)

[0013] The present invention discloses an optical receiving device for receiving a burst optical signal, the optical receiving device comprising: a light receiving element for receiving the optical signal; an amplifier for receiving and amplifying a current based on an input current from the light receiving element; a DC adjustment circuit connected to an input electrical route from the light receiving element to the amplifier for removing an offset current included in the input current; an AC adjustment circuit connected to the input electrical route, a portion of the input current flowing through the AC adjustment circuit; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit comprising: an integrator for integrating the output of the amplifier and outputting it to two electrical routes of a positive phase and a negative phase; and a reverse suppression circuit for operating in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0014] (Station side device)

[0015] The present invention discloses a station-side device connected to a plurality of terminal devices via an optical transmission path utilizing an optical fiber, the station-side device comprising: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier for receiving and amplifying a current based on an input current from the light receiving element; a DC adjustment circuit for connecting to an input electrical path from the light receiving element to the amplifier and removing an offset current contained in the input current; an AC adjustment circuit for connecting to the input electrical path and through which a portion of the input current flows; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit comprising: an integrator for integrating the output of the amplifier and outputting the integrated circuit to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit for operating in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0016] (PON System)

[0017] The PON system disclosed in the present invention comprises: a plurality of terminal devices; an optical transmission path using an optical fiber; and a station-side device, which communicates with the plurality of terminal devices via the optical transmission path, wherein an optical receiving device of at least the station-side device mounted on the terminal device and the station-side device comprises: a light receiving element, which receives a burst optical signal from the terminal device; an amplifier, which receives and amplifies a current based on an input current from the light receiving element; a DC adjustment circuit, which is connected to an input electrical path from the light receiving element to the amplifier and removes an offset current included in the input current; an AC adjustment circuit, which is connected to the input electrical path and a part of the input current flows through the AC adjustment circuit; and a control unit, which controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator, which integrates the output of the amplifier and outputs it to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit, which operates in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0018] (Preamplifier)

[0019] The preamplifier disclosed in the present invention comprises: an amplifier that receives and amplifies a current based on an input current from a photosensitive element that receives a burst optical signal; a DC adjustment circuit that is connected to an input electrical route from the photosensitive element to the amplifier and removes an offset current included in the input current; an AC adjustment circuit that is connected to the input electrical route and through which a portion of the input current flows; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, the control unit comprising: an integrator that integrates the output of the amplifier and outputs it to two electrical routes of a positive phase and a negative phase; and a reverse suppression circuit that operates in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0020] (Light Receiving Method)

[0021] The present invention discloses an optical receiving method for receiving a burst optical signal, wherein, in the pre-amplification stage, a current based on an input current from a photosensitive element is received and amplified by an amplifier, the photosensitive element receives the optical signal, and based on the output of the amplifier and a reference voltage, an offset current contained in the input current is removed, and a part of the input current is released, the output of the amplifier is integrated by an integrator, and output to two electrical routes of a positive phase and an inverted phase, and when the inverted phase potential output to the two electrical routes is higher than the positive phase potential, a current is injected into the positive phase and a current is extracted from the inverted phase.

[0022] (Integrator output reversal suppression method)

[0023] The present invention discloses an output reversal suppression method of an integrator in a preamplifier for light reception, wherein a current based on an input current from a light receiving element is received and amplified, the light receiving element receives a burst light signal, an offset current contained in the input current is removed based on the amplified output and a reference voltage, and a portion of the input current is released, the output is integrated by the integrator and output to two electrical routes of a positive phase and a negative phase, and when the negative phase potential output to the two electrical routes is higher than the positive phase potential, a current is injected into the positive phase and a current is extracted from the negative phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a connection diagram of a PON system according to an embodiment.

[0025] Figure 2 This is a diagram showing an example of a circuit configuration of an optical receiving device, and is a diagram centered particularly on a preamplifier portion.

[0026] Figure 3 Yes means Figure 2 Diagram of the internal circuit of the reverse inhibition circuit.

[0027] Figure 4 This is a graph showing an example of inverted integrator output in an open loop as a result of DC analysis (static characteristics analysis).

[0028] Figure 5 This is a graph showing an example of a delay in transient response due to an integrator output reversal as a result of transient analysis.

[0029] Figure 6 This is a graph showing an example of inverted integrator output in an open loop as a result of DC analysis (static characteristics analysis).

[0030] Figure 7 This is a graph showing an example of the result of transient analysis.

[0031] Figure 8 This is an example of a graph showing how the gain of an amplifier with an added reverse suppression circuit exhibits frequency characteristics with respect to input currents of various magnitudes. DETAILED DESCRIPTION

[0032] [Problems to be Solved by the Present Disclosure]

[0033] If the negative offset voltage applied to the reference voltage increases, the positive and negative outputs of the integrator may be inverted and the potential difference may increase. In this case, the transient response to the burst may be delayed, and the normal reception of the optical signal may fail.

[0034] In view of this problem, an object of the present disclosure is to suppress the inversion of the output of an integrator in an optical receiving device that receives a burst optical signal.

[0035] [Effects of the present disclosure]

[0036] According to the present disclosure, it is possible to suppress the inversion of the output of the integrator in the optical receiving device that receives the burst optical signal.

[0037] [Description of Embodiments of the Present Disclosure]

[0038] The embodiments of the present disclosure include at least the following contents as their gist.

[0039] (1) Disclosed as an optical receiving device is an optical receiving device for receiving a burst optical signal, comprising: a light receiving element for receiving the optical signal; an amplifier for receiving and amplifying a current based on an input current from the light receiving element; a DC adjustment circuit connected to an input electrical path from the light receiving element to the amplifier for removing an offset current included in the input current; an AC adjustment circuit connected to the input electrical path, through which a portion of the input current flows; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit comprising: an integrator for integrating the output of the amplifier and outputting the integrated circuit to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit for operating in a manner of injecting a current into the positive phase and extracting a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

[0040] In such an optical receiving device, when the output of the integrator is reversed and the reverse phase potential becomes higher than the positive phase potential, the reversal suppression circuit can operate in a manner of injecting current into the positive phase and extracting current from the reverse phase. Thus, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator in the optical receiving device that receives a burst optical signal can be suppressed.

[0041] (2) In the optical receiving device of (1) above, it is preferred that the current injected and the current extracted by the reverse suppression circuit are equal to each other.

[0042] In this case, since the injected current and the extracted current are equal to each other, the common potential of the output of the integrator does not change.

[0043] (3) In the optical receiving device of (1) or (2), the inversion suppression circuit may include: a transconductance amplifier that converts the voltage based on the potential difference between the positive phase and the negative phase output by the integrator into a current and outputs it; and a current mirror circuit that generates a current injected into the positive phase and a current extracted from the negative phase based on the output of the transconductance amplifier.

[0044] In this case, when the positive phase potential is higher than the negative phase potential of the integrator output, the inversion suppression circuit neither injects nor extracts current. When the negative phase potential of the integrator output is higher than the positive phase potential, that is, when the potential inversion begins to occur, the current that suppresses this situation can be immediately generated by the current mirror circuit.

[0045] (4) In the optical receiving device according to any one of (1) to (3), for example, a negative offset voltage is added to the reference voltage.

[0046] There is a difference in strength in a burst optical signal. For example, when the strength is relatively weak, if a negative offset voltage is not applied to the reference voltage, even if the positive offset voltage is slightly increased, there is a case where the DC adjustment circuit draws current and causes an increase in noise. Therefore, it is not a good idea to reduce the negative offset voltage, and it is preferable to apply a sufficiently negative offset voltage.

[0047] (5) In the optical receiving device of any one of (1) to (4), for example, when the positive phase potential is higher than the negative phase potential, the inversion suppression circuit does not perform the operation of injecting current into the positive phase and extracting current from the negative phase.

[0048] When the positive phase potential is higher than the negative phase potential, the reverse suppression circuit does not perform useless operations.

[0049] (6) As a station side device, it is a station side device connected to multiple terminal devices via an optical transmission path using an optical fiber, and the station side device includes: a light receiving element that receives a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a DC adjustment circuit that is connected to an input electrical path from the light receiving element to the amplifier and removes an offset current included in the input current; an AC adjustment circuit that is connected to the input electrical path, and a portion of the input current flows through the AC adjustment circuit; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs it to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit that operates in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0050] In such a station-side device, when the output of the integrator is reversed and the reverse-phase potential is higher than the positive-phase potential, the reversal suppression circuit can operate in a manner that injects current into the positive phase and extracts current from the reverse phase. Thus, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator in the station-side device that receives a burst optical signal can be suppressed.

[0051] (7) A PON system comprising: a plurality of terminal devices; an optical transmission path using an optical fiber; and a station-side device for communicating with the plurality of terminal devices via the optical transmission path, wherein an optical receiving device of at least the station-side device mounted on the terminal devices and the station-side device comprises: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier for receiving and amplifying a current based on an input current from the light receiving element; a DC adjustment circuit connected to an input electrical path from the light receiving element to the amplifier for removing an offset current included in the input current; an AC adjustment circuit connected to the input electrical path, a portion of the input current flowing through the AC adjustment circuit; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage, the control unit comprising: an integrator for integrating the output of the amplifier and outputting the integrated circuit to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit for operating in a manner that injects current into the positive phase and extracts current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0052] In such a PON system, in the optical receiving device in the station side device, when the output of the integrator is reversed and the reverse phase potential becomes higher than the positive phase potential, the reversal suppression circuit can operate in a manner of injecting current into the positive phase and extracting current from the reverse phase. As a result, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator in the optical receiving device that receives the burst optical signal can be suppressed.

[0053] (8) As a preamplifier, it comprises: an amplifier that receives and amplifies a current based on an input current from a light receiving element that receives a burst optical signal; a DC adjustment circuit that is connected to an input electrical path from the light receiving element to the amplifier and removes an offset current included in the input current; an AC adjustment circuit that is connected to the input electrical path and through which a portion of the input current flows; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs it to two electrical paths of a positive phase and a negative phase; and a reverse suppression circuit that operates in a manner of injecting current into the positive phase and extracting current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.

[0054] In such a preamplifier, when the output of the integrator is reversed and the reverse phase potential is higher than the positive phase potential, the reversal suppression circuit can operate in a manner that injects current into the positive phase and extracts current from the reverse phase. Thus, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator when receiving a burst optical signal can be suppressed.

[0055] (9) As a light receiving method, it is a light receiving method for receiving a burst light signal, wherein, in the pre-amplification stage, a current based on an input current from a light receiving element is received and amplified by an amplifier, the light receiving element receives the light signal, and based on the output of the amplifier and a reference voltage, an offset current included in the input current is removed and a part of the input current is released, the output of the amplifier is integrated by an integrator and output to two electrical routes of a positive phase and a negative phase, and when the negative phase potential output to the two electrical routes is higher than the positive phase potential, a current is injected into the positive phase and a current is extracted from the negative phase.

[0056] According to such a light receiving method, when the output of the integrator is reversed and becomes a state where the reverse phase potential is higher than the positive phase potential, current can be injected into the positive phase and current can be extracted from the reverse phase. Thus, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator when receiving a burst optical signal can be suppressed.

[0057] (10) As an output reversal suppression method of an integrator, it is an output reversal suppression method of an integrator in a preamplifier for light reception, wherein a current based on an input current from a light receiving element that receives a burst optical signal is received and amplified, an offset current included in the input current is removed based on the amplified output and a reference voltage, and a portion of the input current is released, the output is integrated by the integrator and output to two electrical paths of a positive phase and a negative phase, and when the negative phase potential output to the two electrical paths is higher than the positive phase potential, a current is injected into the positive phase and a current is extracted from the negative phase.

[0058] According to such an output reversal suppression method, when the output of the integrator is reversed and the reverse phase potential is higher than the positive phase potential, current can be injected into the positive phase and current can be extracted from the reverse phase. Thus, the reversal of the output of the integrator is suppressed. Therefore, even when a sufficiently negative offset voltage is applied, the potential difference reversal expansion of the output of the integrator can be suppressed. In this way, the reversal of the output of the integrator in the case of receiving a burst optical signal can be suppressed.

[0059] [Details of the embodiments of the present disclosure]

[0060] Hereinafter, specific examples of the present disclosure will be described with reference to the drawings.

[0061] PON System

[0062] Figure 1 This is a connection diagram of a PON system 100 involved in one embodiment. In the figure, a station-side device (OLT: Optical Line Terminal) 1 is set as a convergence station for multiple terminal devices (ONU: Optical Network Unit) 2, 3, and 4 connected in a P2MP (Point to Multipoint) relationship. The terminal devices 2, 3, and 4 are respectively set in the homes of subscribers of the PON system 100. In this system, an optical fiber network is formed in which one optical fiber (trunk line) 5 connected to the station-side device 1 is branched into multiple optical fibers (branch lines) 7, 8, and 9 via an optical coupler 6. In addition, the number of terminal devices is only an example for the convenience of illustration, and there are more in reality.

[0063] Between the station side device 1 and each terminal device 2, 3, 4, uplink communication from the terminal device 2, 3, 4 to the station side device 1 and downlink communication from the station side device 1 to each terminal device 2, 3, 4 can be performed. The distance from the optical coupler 6 to each terminal device 2, 3, 4 is not uniform, but there is a difference in distance. Therefore, there is a difference in the intensity of the optical signal reaching the station side device 1 from the terminal devices 2, 3, 4. The station side device 1 is equipped with a line card 1a including an optical receiving device.

[0064] Light receiving device

[0065] Figure 2 1 is a diagram showing an example of a circuit configuration of an optical receiving device 10, and is a diagram centered on the preamplifier 11 in particular. The optical receiving device 10 is a device that receives burst optical signals (hereinafter referred to as bursts) transmitted from terminal devices 2, 3, and 4, and includes an avalanche photodiode 12 as a light receiving element, an amplifier 13, a DC adjustment circuit 14, an AC adjustment circuit 15, a control unit 16, a differential circuit 17, a detection circuit 18, and a reference potential generating circuit 19. The output (Vout, Voutb) of the preamplifier 11 is transmitted to a subsequent circuit 21 via AC coupling of a capacitor 2.

[0066] The avalanche photodiode 12, to which the voltage VPD is applied to the cathode, converts the optical signal into a current. The amplifier 13 receives and amplifies the current based on the input current from the avalanche photodiode 12, and outputs the voltage Va. The DC adjustment circuit 14 connected to the input electrical route L from the avalanche photodiode 12 to the amplifier 13 has a current mirror circuit of MOSFET (Metal-Oxide-Semiconductor-Field-Effect-Transistor: Metal-Oxide Semiconductor Field Effect Transistor, hereinafter referred to as MOS transistor) M0 and M1.

[0067] The DC adjustment circuit 14 removes the offset current Iaoc from the input current Iin from the avalanche photodiode 12. Similarly, the AC adjustment circuit 15 connected to the input electrical path L has a MOS transistor M3. The AC adjustment circuit 15 has a function of allowing a part of the current Iin input from the avalanche photodiode 12 (current Iagc) to flow (release) without sending it to the amplifier 13. In this way, the current Iin is divided into the current Iaoc, the current Iagc, and the input current to the amplifier 13.

[0068] The control unit 16 includes an integrator 161, an inversion suppression circuit 162, a transconductance amplifier (hereinafter referred to as OTA (Operational Transconductance Amplifier)) 163, a current control unit 164, and a MOS transistor M2. A reference voltage including a negative offset voltage is supplied from the reference potential generating circuit 19 to the integrator 161, the differential circuit 17, and the MOS transistors M2 and M3. The negative offset voltage allows the AC adjustment circuit 15 and the DC adjustment circuit 14 to operate for a strong input burst, but not for a weak input burst.

[0069] The integrator 161 integrates the output of the amplifier 13 and outputs it to two electrical paths of the positive phase P and the negative phase N. The output of the integrator 161 is provided to the current control unit 164 via the OTA 163. The OTA 163 has a circuit that changes the amplification factor according to the input. The current control unit 164 sets the input current range for adjusting the amplification factor. The detection circuit 18 has a function of detecting the output from the differential circuit 17 and switching the time constant of the integrator 161 in order to cope with a strong input burst. The current control unit 164 controls the current mirror circuit of the MOS transistors M2 and M3 and the current mirror circuit of the MOS transistors M0 and M1.

[0070] Figure 3 Yes means Figure 2 FIG. 1 is a diagram of an internal circuit of the reverse suppression circuit 162. Figure 3 In the embodiment, the reverse suppression circuit 162 includes an OTA 162A, PNP-type MOS transistors M11, M12, and M13 constituting a current mirror circuit 162B, and NPN-type MOS transistors M14 and M15 constituting another current mirror circuit 162C. The control power supply voltage Vcc is supplied to the source side of the MOS transistors M14 and M15. The source side of the MOS transistors M11, M12, and M13 is connected to GND.

[0071] OTA162A operates according to the positive phase potential Vp and the reverse phase potential Vn input from the integrator 161. Specifically, when Vp ≥ Vn, OTA162A does not operate. When the reverse phase potential Vn becomes an inversion state higher than the positive phase potential Vp and the reverse potential difference exceeds a predetermined reference value, OTA162A operates. This action refers to the generation of a positive output current proportional to the potential difference after subtracting the reference value from the reverse potential difference. According to the generated current, the current Ip is injected into the positive phase P and the current In is extracted from the reverse phase N through the current mirror circuit 162B based on MOS transistors M11, M12, and M13 and the current mirror circuit 162C based on MOS transistors M14 and M15.

[0072] In the optical receiving device 10 having such a reversal suppressing circuit 162, when the output of the integrator 161 is reversed and the reverse phase potential Vn becomes higher than the positive phase potential Vp (strictly speaking, higher than the reference value), the reversal suppressing circuit 162 operates in such a manner that a current is injected into the positive phase P and a current is extracted from the reverse phase N. Thus, the reversal of the output of the integrator 161 is suppressed. Therefore, even when a sufficiently negative offset voltage is applied to the reference voltage generated by the reference potential generating circuit 19, the potential difference reversal expansion of the output of the integrator 161 can be suppressed.

[0073] In addition, the same current In also flows through the MOS transistors M11, M12, and M13 by the operation of the current mirror circuit 162B based on the MOS transistors M11, M12, and M13. As a result, a current Ip equal to the current In also flows through the MOS transistor M14, and a current Ip flows through the MOS transistor M15 by the operation of the current mirror circuit 162C based on the MOS transistors M14 and M15. That is, the current Ip injected into the positive phase P and the current In extracted from the negative phase N by the reverse suppression circuit 162 are equal to each other. In this way, since the injected current and the extracted current are equal to each other, the common potential of the output of the integrator 161 does not change.

[0074] In addition, OTA162A of the reversal suppression circuit 162 converts the voltage based on the potential difference between the positive phase and the reverse phase output by the integrator 161 into a current and outputs it. Based on the output of OTA162A, the current mirror circuits 162B and 162C generate a current injected into the positive phase and a current extracted from the reverse phase. In this case, when the positive phase potential Vp is higher than the reverse phase potential Vn output by the integrator 161, the reversal suppression circuit 162 neither injects nor extracts the current. In other words, no useless action is performed. When the reverse phase potential Vn output by the integrator 161 is higher than the positive phase potential Vp, that is, when the potential reversal begins to occur, the current mirror circuits 162B and 162C can immediately generate a current to suppress this situation.

[0075] Hereinafter, the effects of the above-mentioned reverse suppression circuit 162 will be described using graphs. First, for comparison, a case where there is no reverse suppression circuit 162 will be described.

[0076] 《Case without reverse suppression circuit》

[0077] (Integrator output inverts when open loop)

[0078] Figure 4This is a graph showing an example of an inverted integrator output during an open loop as a result of a DC analysis (static characteristic analysis). (a) shows the voltage output by the amplifier 13 (dashed line) and the reference voltage (solid line) to which a negative offset voltage (40 mV) is added. (b) shows the positive phase potential (solid line) and the negative phase potential (dashed line) of the output of the integrator 161. (c) shows the gate potential (dashed line) of the MOS transistor M3 of the AC adjustment circuit 15 and the gate potential (solid line) of the MOS transistors M0 and M1 of the DC adjustment circuit 14. (d) shows the offset current of the DC that has been removed. The horizontal axis is a logarithmic scale of the input current (Iin) common to (a) to (d).

[0079] In the current range with low input current (from 10 -5 [A] to the vertical single-dot dash line in the figure), a negative offset voltage acts, the DC adjustment circuit 14 and the AC adjustment circuit 15 do not function, and no AC and DC currents are extracted from the input current (hereinafter, the extracted current is referred to as "current extraction"). For input currents above the single-dot dash line, the DC adjustment circuit 14 and the AC adjustment circuit 15 extract current. Here, as can be seen from the graph (b), in the case of an input current less than the single-dot dash line, there is a problem that the positive phase potential and the negative phase potential of the output of the integrator 161 are greatly reversed.

[0080] then, Figure 5 1 is a graph showing an example of a delay in transient response caused by an inverted integrator output as a result of transient analysis. In the figure, (a) shows the input current (Iin) of the avalanche photodiode 12 when receiving an optical signal of a weak input burst after a strong input burst. (b) shows the inverted amplified output (burst-like waveform) of the amplifier 13 relative to the input voltage and -40mV (straight-line portion) as a reference voltage. (c) shows the positive phase potential (solid line) and the reverse phase potential (dashed line) of the output of the integrator 161. In (d), the upper line is the source voltage of the MOS transistor M3 for AC current extraction, and the two overlapping lower lines are the gate voltage of the MOS transistor M3 for AC current extraction and the gate voltage of the MOS transistors M0 and M1 for DC current extraction. The lower line is the level of GND. (e) are two lines that are always roughly overlapping, and the one with slight vibrations up and down is the DC extraction current, and the straight-line one is the AC extraction current. (f) shows the input voltage to the subsequent circuit 21. The horizontal axis is the common time from (a) to (f).

[0081] When to pay attention Figure 5When (c) is concerned, it is always in the inversion state. As shown by the dotted line of the ellipse, for a strong input burst, the burst ends when it cannot escape from the inversion state. Therefore, the optical receiving device 10 is in a state where the loop is always open. When (d) is concerned, the lower line is attached to GND and no current is drawn. When (e) is concerned, no current is actually drawn. According to Figure 5 When the output of the integrator 161 is inverted, it may not be able to escape from the inversion, resulting in a delay in transient response.

[0082] In addition, when a negative offset voltage is not applied to the reference voltage, even if a positive offset voltage is slightly increased under PVT (Process-Voltage-Temperature) conditions, a closed loop is formed and current is extracted even if a weak input suddenly occurs, which sometimes causes an increase in noise. Therefore, it is not a good idea to reduce the negative offset voltage, and it is preferable to apply a sufficiently negative offset voltage. In addition, a function is required in which the reversal potential difference between the positive phase potential and the reverse phase potential of the output of the integrator 161 does not increase even if a sufficient negative offset voltage is provided. The reversal suppression circuit 162 is a solution to this requirement.

[0083] 《When there is a reverse suppression circuit》

[0084] Figure 6 This is a graph showing an example of inverted integrator output during open loop as a result of DC analysis (static characteristic analysis). (a) shows the voltage output by amplifier 13 (dashed line) and the reference voltage (solid line) to which a negative offset voltage (40 mV) is added. (b) shows the positive phase potential (solid line) and the negative phase potential (dashed line) of the output of integrator 161. (c) shows the gate potential (dashed line) of MOS transistor M3 of AC adjustment circuit 15 and the gate potential (solid line) of MOS transistors M0 and M1 of DC adjustment circuit 14. (d) shows the offset current of DC that is removed. (e) shows the current injected into the positive phase (solid line) and the current extracted from the negative phase (dashed line, merging with the solid line midway) in order to suppress the output reversal of integrator 161. The horizontal axis is the logarithmic scale of the input current (Iin) common to (a) to (e). The vertical single-point dashed line in the figure shows the position of the input current of about 90 μA.

[0085] like Figure 6 As shown in (e), when the input current is 10μA (10 -5 In the weak input range of 90 μA to 90 μA, current is injected into the positive phase and an equal amount of current is extracted from the negative phase. As a result, as can be seen from the waveform (b), even when a negative offset voltage is applied, a large reversal of the output of the integrator 161 in the weak input range is suppressed.

[0086] Figure 7: is a graph showing an example of the result of transient analysis. In the figure, (a) shows the input current (Iin) of the avalanche photodiode 12 when receiving an optical signal of a weak input burst after a strong input burst. (b) shows the inverted amplified output (burst-like waveform) of the amplifier 13 relative to the input voltage and -40mV (straight line portion) as a reference voltage. (c) shows the positive phase potential (solid line) and the reverse phase potential (dashed line) of the output of the integrator 161. In (d), the upper line is the source voltage of the MOS transistor M3 for AC current extraction, the middle line is the gate voltage of the MOS transistors M0 and M1 for DC current extraction, and the lower line is the gate voltage of the MOS transistor M3 for AC current extraction. In (e), the DC extraction current is the one with the largest change at the top, and the AC extraction current is the straight line at the bottom. (f) shows the input voltage to the subsequent circuit 21. The horizontal axis is the common time from (a) to (f).

[0087] exist Figure 7 In (c), the inversion state is released within about 0.2 μs (= 200 nsec) from the beginning of the initial burst, which is indicated by the dotted circle. Figure 5 By comparison, it can be seen that the delay of transient response is significantly improved and shortened.

[0088] Then, the inverted state of the integrator output is generated for the weak input burst, but the gate voltage of the MOS transistors M0 and M1 of the DC adjustment circuit 14 is maintained, and the closed loop is maintained. In (e), the DC extraction current decreases for the weak input burst and converges to several μA, but the closed loop is maintained.

[0089] Figure 8 This is an example of a graph showing how the gain of the amplifier 13 after adding the reverse suppression circuit 162 shows frequency characteristics for various input currents. The upper double-dashed line frame is enlarged to show the lower graph. The portion surrounded by the dotted ellipse in the lower graph shows that feedback is applied (forming a closed loop) even with a weak input burst of less than 50 μA.

[0090] In terms of noise characteristics, the effective value of the noise is 1.71 μArms when the negative offset voltage is not added and the closed loop operation is performed completely, with respect to the input current (Iin) 24 μA as the integrated value in the frequency band 25 GHz. When the negative offset voltage is added without providing the reverse suppression circuit 162, the effective value of the noise is 1.52 μArms, and the noise is reduced.

[0091] In contrast, when the reverse suppression circuit 162 is provided, the effective value of the noise is 1.54 μA for the same input current. Therefore, even if the reverse suppression circuit 162 is provided, only 0.02 μArms is added, and the noise is sufficiently reduced compared to the case of a completely closed-loop operation. This is considered to be due to the fact that the DC extraction current is as small as several μA when the reverse suppression circuit 162 is used for closed-loop operation.

[0092] As described above, by providing the reverse suppression circuit 162 , in addition to reducing the delay of the transient response, the loop can be continuously closed without increasing noise under the condition that the reference voltage to which the negative offset voltage is added is lower than the output voltage of the amplifier 13 .

[0093] "other"

[0094] Furthermore, the optical receiving device 10 disclosed above is provided in the station-side device 1 , but may also be provided in the terminal devices 2 , 3 , and 4 .

[0095] Supplementary Notes

[0096] The embodiments disclosed herein should be considered in all respects as illustrative rather than restrictive. The scope of the present invention is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0097] Description of Reference Numerals

[0098] 1 station side device

[0099] 1a Line Card

[0100] 2, 3, 4 Terminal Devices

[0101] 5. Fiber Optic

[0102] 6 Optocoupler

[0103] 7, 8, 9 optical fibers

[0104] 10 Light receiving device

[0105] 11 Preamplifier

[0106] 12 Avalanche Photodiode

[0107] 13 Amplifier

[0108] 14 DC regulation circuit

[0109] 15 AC regulation circuit

[0110] 16. Control Unit

[0111] 17 Differential Circuit

[0112] 18 Detection circuit

[0113] 19 Reference potential generating circuit

[0114] 20 Capacitors

[0115] 21 Post-stage circuit

[0116] 100PON System

[0117] 161 Integrator

[0118] 162 reverse suppression circuit

[0119] 162A Transconductance Amplifier (OTA)

[0120] 162B, 162C Current Mirror Circuit

[0121] 163 Transconductance Amplifier (OTA)

[0122] 164 Current Control Unit

[0123] L Input electrical routing

[0124] M0, M1, M2, M3 MOS transistors

[0125] M11, M12, M13, M14, M15 MOS transistors

[0126] N Invert

[0127] P Positive Phase

Claims

1. An optical receiving device for receiving a burst optical signal, wherein: The light receiving device comprises: A light receiving element, receiving the light signal; an amplifier that receives and amplifies a current based on an input current from the light receiving element; A DC adjustment circuit is connected to the input electrical path from the light receiving element to the amplifier, and removes an offset current included in the input current; an AC regulation circuit connected to the input electrical route, wherein a portion of the input current flows through the AC regulation circuit; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, The control unit includes: An integrator integrates the output of the amplifier and outputs it to two electrical paths of positive phase and negative phase; and The reverse suppression circuit operates so as to inject current into the positive phase electrical path and extract current from the negative phase electrical path when the negative phase potential of the output of the integrator is higher than the positive phase potential.

2. The light receiving device according to claim 1, wherein The reverse suppression circuit injects and extracts currents equal to each other.

3. The light receiving device according to claim 1 or 2, wherein: The reverse suppression circuit comprises: a transconductance amplifier that converts the voltage output by the integrator based on the potential difference between the positive phase and the negative phase into a current and outputs the current; and The current mirror circuit generates a current injected into the positive-phase electrical route and a current extracted from the negative-phase electrical route based on the output of the transconductance amplifier.

4. The light receiving device according to claim 1 or 2, wherein: A negative offset voltage is added to the reference voltage.

5. The light receiving device according to claim 3, wherein: A negative offset voltage is added to the reference voltage.

6. The light receiving device according to claim 1 or 2, wherein: When the positive phase potential is higher than the negative phase potential, the reverse suppression circuit does not perform an operation of injecting current into the positive phase electrical path and extracting current from the negative phase electrical path.

7. The light receiving device according to claim 3, wherein: When the positive phase potential is higher than the negative phase potential, the reverse suppression circuit does not perform an operation of injecting current into the positive phase electrical path and extracting current from the negative phase electrical path.

8. The light receiving device according to claim 4, wherein: When the positive phase potential is higher than the negative phase potential, the reverse suppression circuit does not perform an operation of injecting current into the positive phase electrical path and extracting current from the negative phase electrical path.

9. A station-side device connected to a plurality of terminal devices via an optical transmission path using optical fibers, wherein: The station side device comprises: A light receiving element, receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; A DC adjustment circuit is connected to the input electrical path from the light receiving element to the amplifier, and removes an offset current included in the input current; an AC regulation circuit connected to the input electrical route, wherein a portion of the input current flows through the AC regulation circuit; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, The control unit includes: An integrator integrates the output of the amplifier and outputs it to two electrical paths of positive phase and negative phase; and The reverse suppression circuit operates so as to inject current into the positive phase electrical path and extract current from the negative phase electrical path when the negative phase potential of the output of the integrator is higher than the positive phase potential.

10. A PON system comprising: multiple terminal devices; Light transmission paths using optical fibres; and The station side device communicates with the plurality of terminal devices via the optical transmission path, wherein: The optical receiving device of at least the station side device mounted in the terminal device and the station side device comprises: A light receiving element, receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; A DC adjustment circuit is connected to the input electrical path from the light receiving element to the amplifier, and removes an offset current included in the input current; an AC regulation circuit connected to the input electrical route, wherein a portion of the input current flows through the AC regulation circuit; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, The control unit includes: An integrator integrates the output of the amplifier and outputs it to two electrical paths of positive phase and negative phase; and The reverse suppression circuit operates so as to inject current into the positive phase electrical path and extract current from the negative phase electrical path when the negative phase potential of the output of the integrator is higher than the positive phase potential.

11. A preamplifier comprising: an amplifier that receives and amplifies a current based on an input current from a light receiving element that receives a burst-type optical signal; A DC adjustment circuit is connected to the input electrical path from the light receiving element to the amplifier, and removes an offset current included in the input current; an AC regulation circuit connected to the input electrical route, wherein a portion of the input current flows through the AC regulation circuit; and a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and a reference voltage, The control unit includes: An integrator integrates the output of the amplifier and outputs it to two electrical paths of positive phase and negative phase; and The reverse suppression circuit operates so as to inject current into the positive phase electrical path and extract current from the negative phase electrical path when the negative phase potential of the output of the integrator is higher than the positive phase potential.

12. A light receiving method, which is a light receiving method for receiving a burst optical signal, wherein: In the pre-amplification stage, receiving a current based on an input current from a light receiving element that receives the light signal and amplifying the current through an amplifier, Based on the output of the amplifier and a reference voltage, an offset current included in the input current is removed, and a part of the input current is released. The output of the amplifier is integrated by an integrator and output to two electrical routes of positive phase and negative phase. When the negative phase potential output to these two electrical routes is higher than the positive phase potential, current is injected into the positive phase electrical route and current is extracted from the negative phase electrical route.

13. A method for suppressing output reversal of an integrator, which is a method for suppressing output reversal of an integrator in a preamplifier for light reception, wherein: receiving and amplifying a current based on an input current from a light receiving element that receives a burst of optical signals, Based on the amplified output and the reference voltage, the offset current included in the input current is removed, and a part of the input current is released, The amplified output is integrated by the integrator and output to two electrical routes of positive phase and negative phase. When the negative phase potential output to these two electrical routes is higher than the positive phase potential, current is injected into the positive phase electrical route and current is extracted from the negative phase electrical route.

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