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.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 from the photoelectric conversion means 1 to an output end. One of the two transmission lines AL, KL includes opening means 4. 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 to the two transmission lines AL, KL. In a non-power supply state where power is not supplied, the transmission line KL with the opening means 4 is opened by the opening means 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 opened; 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] Patent Document 1, as shown in Figures 9(a) and 9(b), provides a high-frequency transmission path 10 and a low-frequency transmission path 11. The high-frequency signal is returned to the photodiode 2 via the high-frequency transmission path 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 path 10, connected in series to the cathode side of the photodiode D2 and grounded. The coupling capacitor C2 is a high-frequency signal passing means for coupling and passing only the high-frequency signal among the electrical signals output from the photodiode D2. Therefore, a small-capacity capacitor of several 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. Therefore, the impedance to the high-frequency signal increases. When 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 electric signal (FM signal) obtained by photoelectric conversion even when no power is fed, even if the optical input level is high. [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 by an optoelectric conversion means into an electrical signal corresponding to the intensity (light intensity) of the optical signal, 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 devices connected to the output side of each transmission line. Its characteristic is that when the optoelectric conversion means is supplied with voltage from a power supply means, the electrical signal photoelectrically converted by the optoelectric conversion means flows to both of the transmission lines on the output side of the optoelectric conversion means, so that the electrical signal can be received by receiving devices connected to both transmission lines. When no voltage is supplied from the power supply means, one of the transmission lines is opened by an opening means (for example, a switch) to isolate it from the optoelectric conversion means, so that the electrical signal output from the optoelectric conversion means is not transmitted to the opened transmission line but is transmitted to the closed transmission line, so that at least an FM electrical signal can be received by receiving devices connected to that transmission line.

[0010] The optical receiving device of the present invention is an optical receiving device that receives an optical multiplexed signal transmitted through an optical transmission system and converts it into an electrical signal containing both signals. It is characterized in that it comprises: photoelectric conversion means that converts the received optical multiplexed signal into an electrical signal corresponding to the optical intensity of the signal; power supply means that supplies voltage to the photoelectric conversion means; two transmission lines that transmit an electrical signal output from the output side of the photoelectric conversion means, disconnecting means (e.g., a switch) that disconnects one of the transmission lines from the photoelectric conversion means; when power is supplied from the power supply means to the photoelectric conversion means, the electrical signals are transmitted through the two transmission lines, and the electrical signals can be received by receiving devices connected to each of the transmission lines; and when power is not supplied from the power supply means to the photoelectric conversion means, the transmission line equipped with the disconnecting means is opened by the disconnecting means, so that the electrical signal output from one output side of the photoelectric conversion means is not transmitted through that transmission line, and the electrical signal output from the other output side is transmitted through a transmission line not equipped with the disconnecting means, so that at least an FM signal can be received by receiving devices connected to the transmission lines.

[0011] The opening means is preferably a circuit configuration that does not affect the electrical signal being transmitted through the transmission line. The photoelectric conversion means may be a photodiode, and the transmission line on the anode side of the photodiode may be the anode-side transmission line, and the transmission line on the cathode side may be the cathode-side transmission line. [Effects of the Invention]

[0012] The optical receiving method and optical receiving device of the present invention have the following advantages. When no power is supplied, one of the transmission lines on the output side of the photoelectric conversion means is opened by the opening means and separated 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 opened.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). [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a circuit diagram showing an example of an optical receiving device of the present invention, in which an opening means (switch) is provided on a cathode side transmission line. [Figure 2] FIG. 10 is a circuit diagram showing another example of the optical receiving device of the present invention, in which a short circuit is provided in addition to the opening means. [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 according to the present invention, in which the output terminal is one common output terminal and two transmission lines are connected to the common output terminal by switching them with a changeover switch. [Figure 5] FIG. 10 is a circuit diagram showing another example of an optical receiving device of the present invention, in which the output terminal is one common output terminal, and the outputs of two transmission lines are mixed in a mixer and output to the common output terminal. [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 electrical signal converted by photoelectric conversion. [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

[0014] The optical receiving method of the present invention can be implemented by the optical receiving device of the present invention, and therefore, the following describes embodiments of the optical receiving method and the optical receiving device of the present invention together.

[0015] (Embodiment of Optical Receiving Method) In the optical receiving method of the present invention, when a voltage is supplied to the photoelectric conversion means from the power supply means, an electrical signal photoelectrically converted by the photoelectric conversion means 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 a voltage is not supplied to the photoelectric conversion means from the power supply means, one of the transmission lines is opened by the opening means to isolate it from the photoelectric conversion means, and the electrical signal output from the photoelectric conversion means is not output from the opened transmission line but only from the non-open transmission line, allowing at least an FM signal to be received by a receiving device connected to that transmission line.

[0016] (Embodiment 1 of the optical receiving device: Figure 1) Fig. 1 shows an example of an embodiment of an optical receiving device of the present invention. The optical receiving device of Fig. 1 includes a photoelectric conversion means 1 that converts an optical signal into an electrical signal, a power supply means Vcc that supplies power to the photoelectric conversion means 1, a 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 rectifier diode D2, and a coil L1 provided on the two output sides of the photoelectric conversion means 1. Of the two transmission lines AL and KL, the cathode side transmission line KL includes an opening means 4. The opening means 4 is composed of an opening switch SW1, which opens the cathode side transmission line KL when no power is supplied, thereby isolating (disconnecting) it from the photoelectric conversion means 1. 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 the power supply means Vcc via the coil L1, and the anode side is connected in series to the 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 signal and outputs the voltage signal, 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] The open switch SW1 installed on the cathode side transmission line KL closes when power is supplied and automatically switches to open when power is not supplied. When closed when power is supplied, the output from the cathode side of the photodiode D1 output to the cathode side transmission line KL is output to the output terminal OUT1, and when open when power is not supplied, it opens the cathode side transmission line KL, separating it from the cathode side of the photodiode D1 and preventing the output from the cathode side from being output to the output terminal OUT1. The cathode side transmission line KL is also equipped with an amplifier (IC1) and DC blocking capacitors C1 and C2.

[0021] 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 power is not 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.

[0022] [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.

[0023] During power supply, power is also supplied from the power supply means Vcc to the coil L1 and amplifier IC1. At this time, the open switch SW1 is closed. 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.

[0024] [Operation of the optical receiving device in Figure 1 when no power is supplied] If the optical receiving device of Figure 1 loses power from the power supply Vcc (becomes unpowered) due to a commercial power outage or other reasons, the photodiode D1 is no longer reverse-biased, and the open switch SW1 automatically opens. 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 the current-to-voltage conversion circuit (resistor R1) 2. At this time, the rectifier diode D2 becomes forward-biased, reducing its impedance. A free-wheeling 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 free-wheeling circuit 5.

[0025] When power is not supplied, the output transistor that controls the voltage of the power supply circuit (not shown) for the power supply means Vcc is in a cutoff state. Therefore, the current output from the cathode of the rectifier diode D2 (Figure 1) does not flow to the power supply circuit for 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, the open switch SW1 is open, so no current flows through the cathode-side transmission line KL. Instead, the current output from the anode side of the photodiode D1 is output to the output terminal OUT2 from the secondary terminal of the transformer T1 via the capacitor C3 on the anode-side transmission line AL. Because the signal output to the output terminal OUT2 is an FM / RF multiplexed signal, a receiving device connected to the output terminal OUT2 can receive the FM signal even when power is not supplied. Even in this case, the FM signal level does not deteriorate even when the output current increases due to increased light illuminance (Figure 8: this patent).

[0026] (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, with the additional difference that a coupling capacitor C5 and a short-circuit switch SW2 are provided on the cathode-side transmission line KL, outside the power supply line VL. A large capacitance (e.g., several tens of pF or more) is suitable for the coupling capacitor C5. The short-circuit switch SW2 is open when power is supplied and automatically closes when power is not supplied.

[0027] Coupling capacitor C5 couples with the high-frequency electrical signal output from photodiode D1. A capacitor's impedance decreases as its capacitance increases, and decreases as the frequency increases. In Figure 2, a large-capacity capacitor is used for coupling capacitor C5, which reduces the impedance for high frequencies, and prevents a decrease in the output of the photoelectrically converted FM signal (high-frequency signal) even if the optical input level increases when no power is supplied (Figure 8).

[0028] [Operation of the optical receiving device in Figure 2 when power is supplied] In the optical signal device in Figure 2, when power is being supplied, the open switch SW1 is closed and the short-circuit switch SW2 is open, so the current output from the cathode side of photodiode D1 flows to the cathode-side transmission line KL, is amplified by amplifier IC1, and is 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 is 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 no power is supplied, the open switch SW1 automatically opens and the short-circuit switch SW2 automatically closes, grounding (short-circuiting) the cathode-side transmission line KL through the coupling capacitor C5 and short-circuit switch SW2. Therefore, the current output from the cathode side of photodiode D1 does not flow through the cathode-side transmission line KL, and 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. Therefore, even when no power is supplied, the FM / RF signal is output to output terminal OUT2 without any reduction in level, allowing the FM signal to be received by the announcement broadcast receiver connected to output terminal OUT2. Even in this case, the FM signal level does not deteriorate even when the light intensity increases and the output current increases (Figure 8: this patent).

[0030] (Embodiment 3 of the optical receiving device: Figure 3) The basic configuration of the optical receiving device in Figure 3 is the same as that in Figure 1, except that 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 in FIG. 3 has the same basic configuration as that in FIG. 1, and therefore its operation when powered and when not powered is the same as that in FIG.

[0032] (Fourth embodiment of optical receiving device: Figure 4) The optical receiving device of 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 device of Figures 1 to 3 are combined into one 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.

[0033] [Operation of the optical receiving device in Figure 4 when powered and when not powered] The basic operation of the optical receiving device in Figure 4 is the same as that in Figure 3. When power is supplied, either the current flowing in the cathode-side transmission line KL or the anode-side transmission line AL is output to the common output terminal OUT3 through the changeover switch SW3. If the receiving device 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. When power is not supplied, the open switch SW1 is open, so no current flows in the cathode-side transmission line KL, and the current flowing in the anode-side transmission line AL is output to the common output terminal OUT3 through the changeover switch SW3. Therefore, the TV receiver or announcement broadcast receiver connected to the common output terminal OUT3 can receive at least FM signals.

[0034] (Fifth embodiment of optical receiving device: Figure 5) The basic configuration of the optical receiving device in Figure 5 is the same as that in Figure 4. The difference is that a mixer 3 is used instead of the changeover switch SW3 in Figure 4. In this case, the RF / FM mixed electrical signals output from the cathode side transmission line KL and the anode side transmission line AL are mixed in the mixer 3 and output to the common output terminal OUT3.

[0035] [Operation of the optical receiving device in Figure 5 when powered and when not powered] The basic operation of the optical receiving device in Figure 5, both when powered and when unpowered, is the same as that in Figure 4. The difference is that when powered, the currents flowing through the cathode-side transmission line KL and the anode-side transmission line AL are mixed in the mixer 3 and output to the common output terminal OUT3. If the receiving device 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. When unpowered, the open switch SW1 is open, so no current flows through the cathode-side transmission line KL and only through the anode-side transmission line AL. The signals from both transmission lines are mixed in the mixer 3 and output to the common output terminal OUT3. Therefore, a TV receiver or announcement broadcast receiver connected to the common output terminal OUT3 can receive at least FM signals.

[0036] (Embodiment 6 of the optical receiving device: Figure 6) Since the photodiode D1 outputs the same current from both the cathode and anode sides, the configuration of the cathode side transmission line KL and the anode side transmission line AL can be swapped. The optical receiving device in Figure 6 swaps the configuration of the cathode side transmission line KL and the anode side transmission line AL in Figure 1. Specifically, an open switch SW1, amplifier IC1, and DC blocking capacitors C2 and C3 are inserted in the anode side transmission line AL, and capacitor C3 is inserted in the cathode side transmission line KL.

[0037] [Operation of the optical receiving device in Figure 6 when power is supplied] In the optical receiving device of Figure 6, the open switch SW1 is closed during power supply, so that the current output from the cathode of photodiode D1 flows to the cathode-side transmission line KL, and the current output from the anode is output to the anode-side transmission line AL. The electrical signals flowing through the respective transmission lines KL and AL 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.

[0038] [Operation of the optical receiving device in Figure 6 when no power is supplied] When no power is supplied, the open switch SW1 is open, so the current output from the anode of the photodiode D1 does not flow to the anode-side transmission line AL, but the current output from the cathode flows to the cathode-side transmission line KL and is output to the output terminal OUT1. Therefore, even when no power is supplied, the FM signal can at least be received by the receiving device connected to the output terminal OUT1.

[0039] (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, capacitor C3 is inserted in the cathode-side transmission line KL, and an open switch SW1, capacitor C1, amplifier IC1, and capacitor C2 are provided in the anode-side transmission line AL, as well as a coupling capacitor C5 and a short-circuit switch SW2. As in Figure 2, the open switch SW1 closes when power is supplied and automatically opens when power is not supplied, while the short-circuit switch SW2 opens when power is supplied and automatically closes when power is not supplied. As in Figure 2, a large-capacity coupling capacitor C5 is suitable.

[0040] [Operation of the optical receiving device in Figure 7 when power is supplied] In the optical receiving device of Figure 7, when power is supplied, the current output from the cathode of photodiode D1 is output to the cathode side transmission line KL, and the current output from the anode is output to the anode side transmission line AL, and FM signals and RF signals can be received by receiving devices connected to the output terminals OUT1 and OUT2 of the respective transmission lines KL and AL.

[0041] [Operation of the optical receiving device in Figure 7 when no power is supplied] In the optical receiving device in Figure 7, when there is no power supply, the open switch SW1 is open and the short-circuit switch SW2 is closed, so the current output from the anode of photodiode D1 does not flow into the anode-side transmission line AL, but the current output from the cathode flows into the cathode-side transmission line KL and is output to the output terminal OUT1. As a result, FM / RF signals are output to the output terminal OUT1, and at least FM signals can be received by a receiving device connected to the output terminal OUT1. [Industrial Applicability]

[0042] 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]

[0043] 1. Photoelectric conversion means 2 Current-to-voltage conversion circuit 3 mixer 4 Release means 5. Circulation Circuit D1 Photodiode D2 Rectifying diode L1, L2 coils C1, C2, C3 capacitors C5 Coupling Capacitor SW1 Open switch 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 when one of the transmission lines is opened by the opening means, no electric signal is output from that transmission line, and only the other transmission line that is not opened is output, so that at least the FM signal can be received by a receiving device connected to the transmission line that is not opened. An optical receiving method comprising:

2. 2. 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 opened and the other is not opened, so that at least an FM signal is output from the transmission line that is not opened. An optical receiving method comprising:

3. 3. The optical receiving method according to claim 1, 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 no power is supplied and which decreases impedance. 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; one of the two transmission lines has an opening means for opening the transmission line; 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 equipped with the opening means is opened by the opening means, so that no current flows through that transmission line, and current is output only from the other transmission line that is not opened, so that at least the FM signal can be received by a receiving device connected to the transmission line that is not opened. An optical receiving device characterized by:

5. 5. The optical receiving device according to claim 4, the opening means comprises a switch, 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. 8. The optical receiving device according to claim 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:

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