Optical receiving method and optical receiving device

Abstract

To provide an optical reception method configured to prevent reduction in output of photoelectrically converted FM signals even when an optical input level in a non-power supply state is high, and an optical receiver (optical network unit).SOLUTION: An optical receiver includes: photoelectric conversion means 1 which converts received optical signals to electric signals; power supply means Vcc which supplies a voltage to the photoelectric conversion means 1; and two transmission lines AL, KL for transmitting electric signals output by the photoelectric conversion means 1 to an output end. A short-circuit 4 is arranged in one of the two transmission lines. In a power supply state where power is supplied from the power supply means Vcc to the photoelectric conversion means 1, electric signals are output from both transmission lines. In a non-power supply state where power is not supplied, the transmission line KL with the short-circuit 4 is short-circuited by the short-circuit 4; no electric signal is output from the transmission line KL; electric signals are output only from the other transmission line AL which is not short-circuited; and a receiving device connected to the transmission line AL receives at least FM signals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical receiving method and an optical receiving device (ONU: Optical Network Unit) that converts an optical signal transmitted from a transmitting side to a receiving (subscriber) side via an optical transmission network into an electrical signal. [Background technology]

[0002] In a CATV system that uses an optical transmission system, an optical transmitter on the sender's side and an optical receiver on the receiver's side are connected via an optical transmission line. In a CATV system, an FM-RF multiplexed optical signal (hereinafter simply referred to as "optical signal"), which is a multiplexed announcement broadcast signal (FM signal) and television broadcast signal (RF signal), is delivered to the receiver, and the optical signal is converted into an FM-RF multiplexed electrical signal (hereinafter simply referred to as "electrical signal") by the ONU and output, so that it can be received by the receiver's receiving device connected to the output side of the ONU.

[0003] Optical receivers incorporate a photoelectric conversion device that converts optical signals into electrical signals. Photodiodes (PDs) are commonly used for photoelectric conversion devices. By applying a reverse voltage (reverse bias voltage) to the PD, a current (reverse current) proportional to the change in light intensity of the optical energy incident on the PD flows, resulting in photoelectric conversion.

[0004] Since announcement broadcasts are disaster information, emergency information, etc., they must be able to be received through photoelectric conversion even during a commercial power outage (when there is no power supply: when there is reverse bias). Photoelectric conversion devices that enable announcement broadcasts to be received even when there is no power supply have been available for some time (Patent Documents 1 and 2).

[0005] As shown in Figures 9(a) and 9(b), Patent Document 1 provides a high-frequency transmission line 10 and a low-frequency transmission line 11. The high-frequency signal is returned to the photodiode 2 via the high-frequency transmission line 10, thereby avoiding the loss that occurs when the high-frequency signal passes through a current adjustment means. Furthermore, a coupling capacitor C2 is provided in the high-frequency transmission line 10, connected in series to the cathode K of the photodiode 2 and grounded. The coupling capacitor C2 functions as a high-frequency signal passing means for coupling and passing only the high-frequency signal from the electrical signal output from the photodiode 2. Therefore, a small-capacity capacitor of a few pF is used to achieve high impedance in the low frequency range and low impedance in the high frequency range. The coupling capacitor C2 has the effect of returning (looping) the high-frequency signal when no power is supplied, but because it shorts out (grounds) the high-frequency signal when power is supplied, a large-capacity capacitor cannot be used. This increases the impedance to the high-frequency signal, and as the optical input level increases when no power is supplied, the output of the photoelectrically converted FM signal (high-frequency signal) decreases.

[0006] In Patent Document 2, as shown in Figures 10(a) and 10(b), a Schottky barrier diode 11 is mounted on the power supply line to enable high output of the FM signal when no power is supplied, but because the Schottky barrier diode 11 has a very large capacitance and affects the frequency characteristics, it is mounted after passing through an inductor 14. In this case, when power is supplied, even if the optical input level increases, the output of the photoelectrically converted FM signal hardly decreases (curve when power is supplied in Figure 8: conventional / this patent), and the curve is close to the ideal curve (Figure 8). However, when no power is supplied, the output of the photoelectrically converted FM signal decreases as the optical input level increases (curve when no power is supplied in Figure 8: conventional), and the increase in output power is not necessarily sufficient. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-15164 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-213579 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to enable a high output of an electrical signal (FM signal) obtained by photoelectric conversion even when the optical input level is high in the absence of power supply. [Means for solving the problem]

[0009] The optical receiving method of the present invention is an optical receiving method in which an optical signal transmitted through an optical transmission system is converted into an electrical signal corresponding to the intensity (light intensity) of the optical signal by an optoelectric conversion means, and the converted electrical signal is output to both of two transmission lines on the output side of the optoelectric conversion means, so that it can be received by receiving equipment connected to the output side of each transmission line.

[0010] The optical receiving method of the present invention is characterized in that, when power is supplied from the power supply means to the photoelectric conversion means, the electrical signal photoelectrically converted by the photoelectric conversion means flows through both transmission lines on the output side of the photoelectric conversion means, and the electrical signal can be received by a receiving device connected to both transmission lines; when power is not supplied from the power supply means, one of the transmission lines is short-circuited with a short-circuiting circuit equipped with a coupling capacitor and a short-circuiting switch, short-circuiting the photoelectric conversion means, and the electrical signal output from the photoelectric conversion means is not transmitted to the shorted transmission line but is transmitted to the non-shorted transmission line, making it possible to receive at least an FM signal by a receiving device connected to that transmission line.

[0011] The optical receiving device of the present invention is an optical receiving device that receives optical multiplexed signals transmitted through an optical transmission system and converts them into an electrical signal containing both signals. It is characterized in that it comprises: optoelectric conversion means that converts the received optical multiplexed signals into an electrical signal corresponding to the optical intensity of the signals; power supply means that supplies voltage to the optoelectric conversion means; two transmission lines that transmit electrical signals output from the output side of the optoelectric conversion means, and a short-circuit that shorts one of the transmission lines from the optoelectric conversion means; when power is supplied from the power supply means to the optoelectric conversion means, electrical signals are transmitted through both transmission lines, and the electrical signals can be received by receiving devices connected to the transmission lines; when power is not supplied from the power supply means to the optoelectric conversion means, the transmission line with the short-circuit is short-circuited by the short-circuit, so that the electrical signal output from one output side of the optoelectric conversion means is not transmitted through that transmission line, and the electrical signal output from the other output side of the optoelectric conversion means is transmitted through a transmission line without the short-circuit, and at least an FM signal can be received by receiving devices connected to the transmission lines.

[0012] It is desirable to use a large-capacity capacitor as the coupling capacitor rather than a capacitor of about several pF. The photoelectric conversion means may be a photodiode, and an anode-side transmission line may be provided on the anode side of the photodiode, and a cathode-side transmission line may be provided on the cathode side. [Effects of the Invention]

[0013] The optical receiving method and optical receiving device of the present invention have the following advantages. (1) When no power is supplied, one of the transmission lines on the output side of the photoelectric conversion means is short-circuited by a short circuit and short-circuited from the photoelectric conversion means, so the electrical signal output from the photoelectric conversion means does not flow through that transmission line, but flows through the other transmission line that is not short-circuited.As a result, even if the input level of the optical signal increases when no power is supplied, the output level of the FM signal hardly decreases (when no power is supplied in Figure 8: this patent), making it possible to achieve high output close to the ideal curve (Figure 8). (2) Because a large-capacity capacitor can be used as the coupling capacitor, the impedance to high-frequency signals is small, and the output of the photoelectrically converted FM signal (high-frequency signal) does not decrease even if the optical input level is high when no power is supplied (Figure 8). [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a circuit diagram showing an example of an optical receiving device of the present invention, in which a short circuit (a coupling capacitor and a short circuit switch) is provided in a cathode side transmission line. [Figure 2] FIG. 10 is a circuit diagram of another example of the optical receiving device of the present invention, in which a short circuit is provided outside the power supply line. [Figure 3] FIG. 10 is a circuit diagram showing another example of the optical receiving device of the present invention, in which the amplifier is composed of a plurality of diodes. [Figure 4] FIG. 10 is a circuit diagram showing another example of an optical receiving device of the present invention, in which there is one output terminal (common output terminal) and two transmission lines are connected to the common terminal by switching using a switch. [Figure 5] FIG. 10 is a circuit diagram showing another example of an optical receiving device according to the present invention, in which the output terminal is one common output terminal and the outputs of two transmission lines are mixed into the common output terminal by a mixer. [Figure 6] 1. FIG. 4 is a circuit diagram showing another example of the optical receiving device of the present invention, in which the configurations of the anode side transmission line and the cathode side transmission line in FIG. 1 are interchanged. [Figure 7] 3 is a circuit diagram showing another example of the optical receiving device of the present invention, in which the configurations of the anode side transmission line and the cathode side transmission line in FIG. 2 are interchanged. [Figure 8] A comparison of the input strength of an optical signal without power supply and the output level of an FM signal converted from optical to electrical signals. [Figure 9] 1A and 1B are circuit diagrams of a conventional optical receiving device, where (a) is an explanatory diagram when power is supplied and (b) is an explanatory diagram when power is not supplied. [Figure 10] 10A and 10B are circuit diagrams of another conventional optical receiving device, where FIG. 10A is an explanatory diagram when power is supplied and FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the optical receiving method and the optical receiving device of the present invention will be described together. In the optical receiving method of the present invention, when power is supplied from the power supply means to the photoelectric conversion means, the photoelectrically converted electrical signal is transmitted through both of the two transmission lines on the output side of the photoelectric conversion means, and the electrical signal can be received by a receiving device connected to both transmission lines.When power is not supplied, one of the transmission lines is short-circuited, and the electrical signal output from the photoelectric conversion means is not output from the short-circuited transmission line, but is output only from the non-shorted transmission line, so that at least FM electrical signals can be received by a receiving device connected to that transmission line.

[0016] (Embodiment 1 of the optical receiving device: Figure 1) 1 shows an example of an embodiment of an optical receiving device of the present invention. This optical receiving device comprises photoelectric conversion means 1 that converts optical signals into electrical signals, power supply means Vcc that supplies power to the photoelectric conversion means 1, current-voltage conversion means (current-voltage conversion circuit) 2 that converts the current photoelectrically converted by the photoelectric conversion means 1 into a voltage, and transmission lines AL and KL, a rectifying diode D2, and a coil L1 provided on the two output sides of the photoelectric conversion means 1. One of the two transmission lines AL and KL, transmission line KL, is equipped with a short-circuit 4. The short-circuit 4 is composed of a coupling capacitor C5 and a short-circuit switch SW2, and shorts out the transmission line KL to short-circuit the photoelectric conversion means 1 when no power is supplied. OUT1 and OUT2 are output terminals.

[0017] A photodiode D1 is used as the photoelectric conversion means 1. The cathode side of the photodiode D1 is connected to a power supply means Vcc via a coil L1, and the anode side is connected in series to a current-voltage conversion circuit 2. The photoelectric conversion means 1 may be anything other than a photodiode as long as it is capable of photoelectric conversion. The anode side of the photodiode D1 is grounded via the current-voltage conversion circuit 2, and the cathode side is connected to the power supply means Vcc and the coils L1 and L2, forming a reflux circuit 5 that refluxes the current output from the anode to the cathode of the photodiode D1 via the current-voltage conversion circuit 2.

[0018] 1 converts the current output from the photodiode D1 into a voltage and outputs the voltage, and uses a resistor R1. The current-voltage conversion circuit 2 may have a different configuration.

[0019] The two transmission lines AL and KL in Fig. 1 transmit the electrical signals photoelectrically converted by the photoelectric conversion means 1 to the output terminals OUT1 and OUT2. In Fig. 1, where a photodiode D1 is used as the photoelectric conversion means 1, the cathode side of the photodiode D1 is the cathode side transmission line KL, and the anode side is the anode side transmission line AL.

[0020] Coupling capacitor C5 is used to couple high-frequency signals from the electrical signal output by photodiode D1. A suitable coupling capacitor C5 has a large capacitance of several tens of pF or more, rather than a few pF. A capacitor's impedance decreases as its capacitance increases. In the present invention, by using a large-capacity capacitor for coupling capacitor C5, the impedance to high-frequency signals decreases, and the output of the photoelectrically converted FM signal (high-frequency signal) does not decrease even if the optical input level increases when no power is supplied (Figure 8).

[0021] The short-circuit switch SW2 forms short-circuit circuit 4 in combination with coupling capacitor C5. The short-circuit switch SW2 is installed on the cathode side transmission line KL together with the amplifier (IC1) and DC-cut capacitors C1 and C2. The short-circuit switch SW2 is open when power is supplied and automatically switches to closed when power is not supplied. When open when power is supplied, the output from the cathode side of photodiode D1, which is output to the cathode side transmission line KL, is output to output terminal OUT1, and when closed when power is not supplied, the cathode side transmission line KL is grounded (shorted), the electrical signal coupled by coupling capacitor C5 is grounded (shorted), and is not output to output terminal OUT1.

[0022] A Schottky barrier diode, for example, can be used for the rectifier diode D2 in Figure 1. When power is supplied from the power supply means Vcc, the rectifier diode D2 is in a reverse bias state, increasing its impedance, and when no voltage is supplied, it is in a forward bias state, decreasing its impedance. The rectifier diode D2 can also be configured by connecting the base and emitter of a bipolar transistor, or by connecting the gate and source of an FET. It can also be an integrated circuit in which multiple diodes are integrated.

[0023] [Operation of the optical receiving device in Figure 1 when power is supplied] Various power sources can be used for the power supply means Vcc in Figure 1, but for example, it can be generated by stepping down and rectifying commercial power. When the commercial power supply is normal, the voltage of the power supply means Vcc is applied as a reverse voltage to the rectifying diode D2 and photodiode D1, and the power is supplied.

[0024] During power supply, power is also supplied from the power supply means Vcc to the coil L1 and amplifier IC1. At this time, the short-circuit switch SW2 is open. In this state, when an optical signal transmitted via an optical transmission network (not shown) is input to the photodiode D1, the photodiode D1 outputs an electrical signal (current) corresponding to the optical input level. As the optical input level increases (strengthens), the output current increases accordingly. As the output current changes, the current flowing through the current-voltage conversion circuit 2 also changes. The current-voltage conversion circuit 2 converts the current output from the anode side of the photodiode D1 into a voltage. The output current from the anode side of the photodiode D1 is output to output terminal OUT2 via the anode-side transmission line AL, and the output current from the cathode side is output to output terminal OUT1 via the cathode-side transmission line KL. The current flowing through the cathode-side transmission line KL is amplified by amplifier IC1 and output to output terminal OUT1. The signals output to output terminals OUT1 and OUT2 are FM / RF multiplexed signals, so the RF signal can be received by a TV receiver connected to output terminal OUT1, and the FM signal can be received by an announcement broadcast receiver connected to output terminal OUT2.

[0025] [Operation of the optical receiving device in Figure 1 when no power is supplied] When the optical receiving device of Figure 1 is powered off due to a commercial power outage or other reasons, the photodiode D1 is no longer reverse-biased, and the short-circuit switch SW2 automatically closes. When light is input to the photodiode D1 in this state, a current corresponding to the input light level is output from the anode of the photodiode D1. This current is applied to the anode of the rectifier diode D2 via resistor R1 of the current-voltage conversion circuit 2, transformer T1, and coil L1. At this time, the rectifier diode D2 is forward-biased, reducing its impedance. A closed circuit (freewheel circuit) 5 is formed by the photodiode D1, transformer T1, resistor R1, capacitor C4, rectifier diode D2, and coil L1, and the current output from the anode of the photodiode D1 flows back to the cathode of the photodiode D1 via this freewheel circuit 5.

[0026] When power is not supplied, the output transistor that controls the voltage of the power supply circuit (not shown) of the power supply means Vcc is in a cutoff state. Therefore, the current output from the cathode of the rectifier diode D2 in Figure 1 does not flow to the power supply circuit side of the power supply means Vcc, and almost all of the current output from the anode of the photodiode D1 returns to the cathode of the photodiode D1. At this time, because the short-circuit switch SW2 is closed, the returned current is grounded (shorted) through the coupling capacitor C5 and short-circuit switch SW2 and does not flow to the cathode-side transmission line KL. At this time, the current output from the anode side of the photodiode D1 is output to the output terminal OUT2 from the output terminal (secondary terminal) of the transformer T1 via the coupling capacitor C3 of the anode-side transmission line AL. Because the signal output to the output terminal OUT2 is an FM / RF multiplexed signal, the FM signal can be received by an announcement broadcast receiver connected to the output terminal OUT2, even when power is not supplied.

[0027] (Optical receiving device embodiment 2: Figure 2) Figure 2 shows a second embodiment of the optical receiving device of the present invention. Its basic configuration is the same as that of Figure 1, except that the coupling capacitor C5 and short-circuit switch SW2 of the cathode-side transmission line KL in Figure 2 are placed outside the power supply line VL. As in Figure 1, a large-capacity coupling capacitor is suitable for the coupling capacitor C5. As in Figure 1, the short-circuit switch SW2 is open when power is supplied and automatically switches to closed when power is not supplied.

[0028] [Operation of the optical receiving device in Figure 2 when power is supplied] The operation of the optical signal device in Figure 2 when powered and when not powered is the same as that in Figure 1. That is, when powered, the short-circuit switch SW2 is open, so the current output from the cathode side of photodiode D1 and flowing through the cathode-side transmission line KL is amplified by amplifier IC1 and output to output terminal OUT1, allowing the TV receiver connected to output terminal OUT1 to receive the RF signal. The current output from the anode side of photodiode D1 flows from the secondary side of transformer T1 to the anode-side transmission line AL and output to output terminal OUT2, allowing the FM signal to be received by the announcement broadcast receiver connected to output terminal OUT2.

[0029] [Operation of the optical receiving device in Figure 2 when no power is supplied] When there is no power supply, the short-circuit switch SW2 closes automatically, and the cathode side transmission line KL is grounded (shorted) through the coupling capacitor C5 and short-circuit switch SW2. As a result, the current output from the cathode side of photodiode D1 is not output to the cathode side transmission line KL, but the current output from the anode of photodiode D1 flows from the secondary side of transformer T1 to the anode side transmission line AL and is output to output terminal OUT2. As a result, even when there is no power supply, the FM / RF signal is output to output terminal OUT2 without any reduction in level, allowing the FM signal to be received by an announcement broadcast receiver connected to output terminal OUT2.

[0030] (Embodiment 3 of the optical receiving device: Figure 3) The optical receiving device in Figure 1 uses only one amplifier IC1, but Figure 3 shows an example in which multiple amplifiers IC1, IC2, IC3, etc. are connected in multiple stages. Amplifier IC1 can also be an integrated circuit equipped with multiple amplifiers IC1, IC2, IC3, etc.

[0031] [Operation of the optical receiving device in Figure 3 when powered and when not powered] The optical receiving device of Figure 3 has the same basic configuration as that of Figure 1, with the only difference being that it has multiple amplifiers IC1. Therefore, the operation of the optical receiving device of Figure 3 when powered and when not powered is the same as that of Figure 1.

[0032] (Fourth embodiment of optical receiving device: Figure 4) The optical receiving device in Figure 4 is a common output terminal type, in which the output terminal OUT1 for RF signal output and the output terminal OUT2 for FM signal output of the optical receiving devices in Figures 1 to 3 are combined into a single output terminal (common output terminal) OUT3, and by switching the selector switch SW3, either the current output from the cathode side transmission line KL or the current output from the anode side transmission line AL can be output to the common output terminal OUT3. The operation of the optical receiving device in Figure 4 up to the selector switch SW3 when powered and when not powered is the same as in Figures 1 to 3. Therefore, if the receiver connected to the common output terminal OUT3 is a TV receiver, it can receive both RF signals and FM signals, and if it is an announcement broadcast receiver, it can receive FM signals.

[0033] (Fifth embodiment of optical receiving device: Figure 5) The optical receiving device in Figure 5 uses a mixer 3 instead of the change-over switch SW3 in Figure 4. In this case, the output from the cathode side transmission line KL and the output from the anode side transmission line AL are mixed in the mixer 3, and an RF / FM mixed electrical signal is output to the common output terminal OUT3. The operation up to the change-over switch SW3 when the optical receiving device in Figure 5 is powered and when it is not powered is the same as in Figure 4. Therefore, if the receiver connected to the common output terminal OUT3 is a TV receiver, it can receive both RF and FM signals, and if it is an announcement broadcast receiver, it can receive FM signals.

[0034] (Embodiment 6 of the optical receiving device: Figure 6) In the embodiments shown in Figures 1 and 2, the cathode-side transmission line KL includes a coupling capacitor C5, an amplifier IC1, and DC-blocking capacitors C2 and C3. However, because the same current is output from both the cathode and anode sides of the photodiode D1, the configurations of the cathode-side transmission line KL and the anode-side transmission line AL can be interchanged. The optical receiver shown in Figure 6 interchanges the configurations of the cathode-side transmission line KL and the anode-side transmission line AL shown in Figure 1. Specifically, the anode-side transmission line AL includes a coupling capacitor C5, a short-circuit switch SW2, a capacitor C1, an amplifier IC1, and a capacitor C2, and the cathode-side transmission line KL includes a capacitor C3. As in Figure 3, the short-circuit switch SW2 opens when power is applied and automatically closes when power is not applied. As in Figure 2, a large-capacity coupling capacitor C5 is suitable.

[0035] [Operation of the optical receiving device in Figure 6 when power is supplied] The operation of the optical receiving device in Figure 6 when powered is the same as that in Figure 1. The current photoelectrically converted by photodiode D1 is output from the cathode to the cathode-side transmission line KL and from the anode to the anode-side transmission line AL. The electrical signals flowing through each transmission line are output to output terminals OUT1 and OUT2, and FM and RF signals can be received by receiving devices connected to these output terminals OUT1 and OUT2.

[0036] [Operation of the optical receiving device in Figure 6 when no power is supplied] The operation of the optical receiving device in Figure 6 when no power is supplied is the same as that of the optical receiving device in Figure 1 when no power is supplied. When no power is supplied, the short-circuit switch SW2 is closed and the anode-side transmission line AL is short-circuited, so the current photoelectrically converted by the photodiode D1 does not flow through the anode-side transmission line AL equipped with the coupling capacitor C5 and short-circuit switch SW2, but flows only through the cathode-side transmission line KL and is output to the output terminal OUT1. As a result, the announcement broadcast receiver connected to the output terminal OUT1 can at least receive FM signals.

[0037] (Seventh embodiment of optical receiving device: Figure 7) The embodiment in Figure 7 swaps the configuration of the cathode side transmission line KL and the anode side transmission line AL in Figure 2. Specifically, the anode side transmission line AL is provided with a coupling capacitor C5, a short-circuit switch SW2, a capacitor C1, an amplifier IC1, and a capacitor C2, and the cathode side transmission line KL is provided with a capacitor C3. As in the case of Figure 2, the short-circuit switch SW2 opens when power is supplied and automatically closes when power is not supplied. As in the case of Figure 2, a large-capacity coupling capacitor C5 is suitable.

[0038] [Operation of the optical receiving device in Figure 7 when power is supplied] The operation of the optical receiving device in Figure 7 when powered is the same as in Figure 2. The current photoelectrically converted by photodiode D1 is output from the cathode to the cathode side transmission line KL and from the anode to the anode side transmission line AL, and FM and RF signals are output to output terminals OUT1 and OUT2 connected to the respective transmission lines, allowing the FM and RF signals to be received by receiving devices connected to the respective output terminals OUT1 and OUT2.

[0039] [Operation of the optical receiving device in Figure 7 when no power is supplied] The operation of the optical receiving device in Figure 7 when no power is supplied is the same as the operation of the optical receiving device in Figure 2 when no power is supplied. When no power is supplied, the short-circuit switch SW2 is closed and the anode side transmission line AL is short-circuited, so the current photoelectrically converted by the photodiode D1 does not flow through the anode side transmission line AL equipped with the coupling capacitor C5 and short-circuit switch SW2, but is output only to the cathode side transmission line KL, an FM / RF signal is output to the output terminal OUT1 of the cathode side transmission line KL, and at least the FM signal can be received by the announcement broadcast receiver connected to the output terminal OUT1. [Industrial Applicability]

[0040] The above-described embodiments are merely examples of the present invention, and the present invention is not limited to these embodiments, and design changes are possible within the scope of the invention's objectives. [Explanation of symbols]

[0041] 1. Photoelectric conversion means 2 Current-to-voltage conversion circuit 3 mixer 4. Short Circuit 5. Circulation Circuit D1 Photodiode D2 Rectifying diode L1, L2 coils C1, C2, C3 capacitors C5 Coupling Capacitor SW2 Shorting switch SW3 selector switch AL transmission line (anode side transmission line) KL transmission line (cathode side transmission line) VL Power supply line Vcc power supply means OUT1 output terminal OUT2 output terminal OUT3 common output terminal

Claims

1. 1. An optical receiving method for converting an optical signal including an FM signal and an RF signal into an electrical signal including both signals by photoelectric conversion using a photoelectric conversion means, When the photoelectric conversion means is supplied with a power supply voltage, the photoelectric conversion means converts the optical signal into an electrical signal and outputs the electrical signal to both of the two transmission lines connected to the two output sides of the photoelectric conversion means, and both or either of the FM signal and the RF signal can be received by receiving devices connected to the output ends of the respective transmission lines; When there is no power supply, that is, when no power supply voltage is supplied to the photoelectric conversion means, the photoelectric conversion means converts an optical signal into an electric signal and outputs the electric signal to both of the two transmission lines connected to the two output sides of the photoelectric conversion means, but one of the transmission lines is short-circuited by a short-circuit circuit formed by a combination of a coupling capacitor and a short-circuit switch, so that no electric signal is output from that transmission line, and only the other transmission line that is not short-circuited is output, so that at least an FM signal can be received by a receiving device connected to the transmission line that is not short-circuited. An optical receiving method comprising:

2. An optical receiving method for converting an optical signal including an FM signal and an RF signal into an electrical signal including both signals by photoelectric conversion using a photoelectric conversion means, When the photoelectric conversion means is supplied with a power supply voltage, the photoelectric conversion means converts the optical signal into an electrical signal and outputs the electrical signal to both of the two transmission lines connected to the two output sides of the photoelectric conversion means, and both or either of the FM signal and the RF signal can be received by receiving devices connected to the output ends of the respective transmission lines; When there is no power supply, that is, when no power supply voltage is supplied to the photoelectric conversion means, the photoelectric conversion means converts an optical signal into an electric signal and outputs the electric signal to both of the two transmission lines connected to the two output sides of the photoelectric conversion means, but one of the transmission lines is short-circuited by a short circuit, so that no electric signal is output from that transmission line, and only the other transmission line that is not short-circuited is output, so that at least the FM signal can be received by a receiving device connected to the transmission line that is not short-circuited, The current output from the photoelectric conversion means is returned to the photoelectric conversion means through a return means which is in a reverse bias state when power is supplied and which increases impedance, and which is in a forward bias state when power is not supplied and which decreases impedance. An optical receiving method comprising:

3. 3. The optical receiving method according to claim 1, The photoelectric conversion means is a photodiode, one of the two transmission lines is an anode side transmission line connected to the anode side of the photodiode, and the other is a cathode side transmission line connected to the cathode side of the photodiode, and when power is supplied, an electric signal output from the anode side of the photodiode is output to the anode side transmission line, and an electric signal output from the cathode side is output to the cathode side transmission line, and when power is not supplied, one of the anode side transmission line or the cathode side transmission line is short-circuited and the other is not short-circuited, so that at least an FM electric signal is output from the transmission line that is not short-circuited. An optical receiving method comprising:

4. An optical receiving device having a photoelectric conversion means for receiving an optical signal including an FM signal and an RF signal and converting the optical signal into an electrical signal including both signals, photoelectric conversion means for converting the optical signal into an electric current; a power supply means for supplying a voltage to the photoelectric conversion means; two transmission lines for transmitting currents output from the two output sides of the photoelectric conversion means; There is a short circuit in one of the two transmission lines, When power is supplied from the power supply means to the photoelectric conversion means, current is output to the two transmission lines, When there is no power supply from the power supply means to the photoelectric conversion means, the transmission line having the short circuit is shorted by the short circuit, so that no current flows through that transmission line, and current is output only from the other transmission line that is not shorted, so that at least the FM signal can be received by a receiving device connected to the transmission line that is not shorted, The short circuit consists of a combination of a coupling capacitor and a short switch. An optical receiving device characterized by:

5. An optical receiving device having photoelectric conversion means for receiving an optical signal including an FM signal and an RF signal and converting it into an electrical signal including both signals, photoelectric conversion means for converting the optical signal into an electric current; a power supply means for supplying a voltage to the photoelectric conversion means; two transmission lines for transmitting currents output from the two output sides of the photoelectric conversion means; There is a short circuit in one of the two transmission lines, The short circuit is made up of a combination of a coupling capacitor and a short switch. When power is supplied from the power supply means to the photoelectric conversion means, current is output to the two transmission lines, When there is no power supply from the power supply means to the photoelectric conversion means, the transmission line having the short circuit is shorted by the short circuit, so that no current flows through that transmission line, and current is output only from the other transmission line that is not shorted, so that at least the FM signal can be received by a receiving device connected to the transmission line that is not shorted, a return means for returning the current output from the photoelectric conversion means to the photoelectric conversion means, the return means being in a reverse bias state when power is supplied and increasing the impedance, and being in a forward bias state when power is not supplied and decreasing the impedance; An optical receiving device characterized by:

6. 6. The optical receiving device according to claim 4, the photoelectric conversion means is a photodiode, one transmission line is an anode-side transmission line that transmits an electrical signal output from the anode side of the photodiode, and the other transmission line is a cathode-side transmission line that transmits an electrical signal output from the cathode side of the photodiode; An optical receiving device characterized by:

7. 7. The optical receiving device according to claim 4, a current-voltage conversion means connected in series to the photoelectric conversion means for converting a current from the photoelectric conversion means into a voltage and outputting the voltage; An optical receiving device characterized by:

8. An optical receiving device according to any one of claims 4 to 7, a rectifying means connected in parallel to the photoelectric conversion means and the current-voltage conversion means; The rectifying means is in a reverse bias state when power is supplied from the power supply means, and impedance increases, and is in a forward bias state when no power is supplied, and impedance decreases. An optical receiving device characterized by:

9. An optical receiving device according to any one of claims 4 to 8, the short circuit is connected to one of the two transmission lines on the output end side or on the opposite side to the output end side of the power supply line that supplies power from the power supply means to the photoelectric conversion means; An optical receiving device characterized by:

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