JP2023006707A - Optical reception method and optical receiver - Google Patents

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

The present invention provides an optical receiving method and an optical receiving apparatus (optical network unit: ONU) for converting an optical signal transmitted from a transmitting side to a receiver (subscriber) side via an optical transmission network into an electrical signal. ).

In a CATV system employing an optical transmission system, an optical transmitter on the sender side and an optical receiver on the receiver side are connected via an optical transmission line. In the CATV system, an FM/RF multiplexed optical signal (hereinafter simply referred to as "optical signal") obtained by multiplexing an announcement broadcast signal (FM signal) and a television broadcast signal (RF signal) is distributed to the receiver side, and the optical signal The ONU converts the signal into an FM/RF multiplexed electrical signal (hereinafter simply referred to as "electrical signal") and outputs it so that it can be received by the receiving equipment on the receiver side connected to the output side of the ONU. .

An optical receiver incorporates a photoelectric conversion device that converts an optical signal into an electrical signal. Photodiodes (PDs) are generally used in photoelectric conversion devices. By applying a reverse voltage (reverse bias voltage) to the PD, a current (reverse current) proportional to the change in the light intensity of the light energy incident on the PD flows and is photoelectrically converted.

Since the notification broadcast is a broadcast of disaster information, emergency information, etc., it is necessary to be able to receive it by photoelectric conversion even when the commercial power supply is cut off (when no power is supplied: when reverse biased). Conventionally, there is a photoelectric conversion device capable of receiving an announcement broadcast even when power is not supplied (Patent Documents 1 and 2).

In Patent Document 1, a high frequency transmission line 10 and a low frequency transmission line 11 are provided as shown in FIGS. , to avoid the loss that occurs when the high-frequency signal passes through the current adjusting means. A coupling capacitor C2 is provided in the high frequency transmission line 10, and the coupling capacitor C2 is connected in series to the cathode side of the photodiode D2 and grounded. The coupling capacitor C2 is high-frequency signal passing means for coupling and passing only high-frequency signals out of the electrical signals output from the photodiode D2. A capacitor with a small capacity of several pF is used so that the The coupling capacitor C2 has the effect of circulating (looping) the high-frequency signal when no power is supplied, but grounds (short-circuits) the high-frequency signal when power is supplied, so a large-capacity capacitor cannot be used. Therefore, when the impedance for high-frequency signals increases and the optical input level increases when no power is supplied, the output of the photoelectrically converted FM signal (high-frequency signal) decreases.

Patent Document 2, as shown in FIGS. 10A and 10B, implements a Schottky barrier diode 11 in a power supply line to enable high output of an FM signal when no power is supplied. Since the capacitance is very large and affects the frequency characteristics, it is mounted after passing through the 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 at power supply in FIG. 8: conventional/patent), and is close to the ideal curve (FIG. 8). 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 FIG. 8: conventional), and the increase in output is not always sufficient.

JP 2011-15164 A JP 2016-213579 A

An object of the present invention is to make it possible to increase the output of a photoelectrically converted electrical signal (FM signal) even when the optical input level is high when power is not supplied.

In the optical receiving method of the present invention, an optical signal transmitted in an optical transmission system is converted into an electrical signal corresponding to the intensity of the optical signal (optical intensity) by a photoelectric conversion means, and the converted electrical signal is transferred to the photoelectric conversion means. This is an optical receiving method that outputs to both of the two transmission lines on the output side so that it can be received by a receiving device connected to the output side of each transmission line. The feature is that when the photoelectric conversion means is supplied with a voltage from the power supply means, the electric signal photoelectrically converted by the photoelectric conversion means flows through both transmission lines on the output side of the photoelectric conversion means, and flows through both transmission lines. An electrical signal can be received by the connected receiving device, and 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) and separated from the photoelectric conversion means. , the electrical signal output from the photoelectric conversion means is not transmitted to the open transmission line, but is transmitted to the open transmission line, so that at least the FM electrical signal can be received by the receiving device connected to the transmission line. This is what I did.

The optical receiver of the present invention is an optical receiver that receives an optical multiplexed signal transmitted in an optical transmission system and converts it into an electrical signal containing both signals. It is characterized by photoelectric conversion means for converting a received optical multiplexed signal into an electrical signal corresponding to its light intensity, power supply means for supplying voltage to the photoelectric conversion means, and electricity output from the output side of the photoelectric conversion means. Two transmission lines for transmitting signals are provided, opening means (for example, a switch) for separating one of the transmission lines from the photoelectric conversion means, and two transmissions when power is supplied from the power supply means to the photoelectric conversion means. Electrical signals are transmitted through the lines, and the electrical signals can be received by receiving devices connected to the respective transmission lines, and the opening means is used when no power supply is supplied from the power supply means to the photoelectric conversion means. The electrical signal output from one output side of the photoelectric conversion means is not transmitted through the transmission line when the provided transmission line is opened by the opening means, and the electrical signal output from the other output side is provided with the opening means. The purpose is to enable at least the FM signal to be received by a receiving device connected to the transmission line, which is transmitted through a transmission line that does not exist.

It is desirable that the opening means have a circuit configuration that does not affect the electrical signal being transmitted on the transmission line. The photoelectric conversion means can be a photodiode, the transmission line on the anode side of the photodiode can be the anode transmission line, and the transmission line on the cathode side can be the cathode transmission line.

The optical receiving method and optical receiving apparatus of the present invention have the following effects.
When no power is supplied, the transmission line on one output side of the photoelectric conversion means is opened by the opening means and separated from the photoelectric conversion means. flow to the other transmission line. For this reason, even if the input level of the optical signal becomes high when no power is supplied, the output level of the FM signal is hardly reduced (when no power is supplied in Fig. 8: this patent), and the output is increased close to the ideal curve (Fig. 8). It becomes possible.

FIG. 2 is a circuit diagram showing an example of the optical receiver according to the present invention when opening means (switch) is provided in the transmission line on the cathode side; FIG. 10 is a circuit diagram of another example of the optical receiver according to the present invention, in which a short circuit is provided in addition to the opening means; FIG. 10 is a circuit diagram of another example of the optical receiver according to the present invention, in which the amplifier is composed of a plurality of diodes; FIG. 10 is a circuit diagram of another example of the optical receiver of the present invention, in which the output terminal is one common output terminal, and two transmission lines are switched by a changeover switch and connected to the common output terminal. FIG. 10 is a circuit diagram of another example of the optical receiver of the present invention, in which the output terminal is one common output terminal, and the outputs of two transmission lines are mixed by a mixer and output to the common output terminal. FIG. 4 is a circuit diagram of another example of the optical receiver according to the present invention, in which the configurations of the anode-side transmission line and the cathode-side transmission line in FIG. 1 are interchanged; FIG. 3 is a circuit diagram of another example of the optical receiver according to the present invention, in which the configurations of the anode-side transmission line and the cathode-side transmission line in FIG. 2 are interchanged; FIG. 3 is a characteristic comparison diagram of the input intensity of an optical signal and the output level of a photoelectrically converted FM electric signal when power is not supplied. It is a circuit diagram of a conventional optical receiver, (a) is an explanatory diagram when power is supplied, and (b) is an explanatory diagram when power is not supplied. It is a circuit diagram of another conventional optical receiver, (a) is an explanatory diagram when power is supplied, and (b) is an explanatory diagram when power is not supplied.

Since the optical receiving method of the present invention can be implemented by the optical receiving apparatus of the present invention, embodiments of the optical receiving method and the optical receiving apparatus of the present invention will be described together below.

(Embodiment of Optical Reception 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, the electric 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. Then, the electrical signal can be received by receiving equipment connected to both transmission lines. When the photoelectric conversion means is not supplied with voltage from the power supply means, one of the transmission lines is opened by the opening means to be separated from the photoelectric conversion means, and the electric signal output from the photoelectric conversion means is transmitted from the opened transmission line. is not output and is output only from a 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.

(Embodiment 1 of Optical Receiver: FIG. 1)
FIG. 1 is an example of an embodiment of an optical receiver according to the present invention. The optical receiver shown in FIG. 1 includes a photoelectric conversion means 1 for converting an optical signal into an electric signal, a power supply means Vcc for supplying power to the photoelectric conversion means 1, and a current photoelectrically converted by the photoelectric conversion means 1 and converted into a voltage. It comprises a current-voltage conversion means (current-voltage conversion circuit) 2, transmission lines AL and KL provided on two output sides of the photoelectric conversion means 1, a rectifying diode D2, and a coil L1. One cathode-side transmission line KL of the transmission lines AL and KL is provided with opening means 4 . The opening means 4 is composed of an opening switch SW1, and disconnects (disconnects) the cathode-side transmission line KL from the photoelectric conversion means 1 by opening it when power is not supplied. OUT1 and OUT2 are output terminals.

A photodiode D1 is used for the photoelectric conversion means 1 . The cathode side of the photodiode D1 is connected to the power supply means Vcc through the coil L1, and the anode side is connected to the current-voltage conversion circuit 2 in series. The photoelectric conversion means 1 may be anything other than a photodiode as long as it is capable of photoelectric conversion. The photodiode D1 has an anode side grounded through the current-voltage conversion circuit 2 and a cathode side connected to the power supply means Vcc and the coils L1 and L2. A freewheeling circuit 5 is configured to return to the cathode of the diode D1.

The current-voltage conversion circuit 2 in FIG. 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 other configurations.

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, in which the 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 thereof is the anode side transmission line AL.

An open switch SW1 provided on the cathode-side transmission line KL is closed when power is supplied, and is automatically switched to open when power is not supplied. The output from the cathode side of the photodiode D1, which is output to the cathode-side transmission line KL when closed when power is supplied, is output to the output terminal OUT1, and when opened when no power is supplied, the cathode-side transmission line KL is opened to open the cathode side of the photodiode D1. , so that the output from the cathode side is not output to the output terminal OUT1. The cathode-side transmission line KL is also provided with an amplifier (IC1) and DC cut capacitors C1 and C2.

A Schottky barrier diode, for example, can be used for the rectifying diode D2 in FIG. The rectifying diode D2 is in a reverse-biased state with an increased impedance when a voltage is supplied from the power supply means Vcc, and is in a forward-biased state with a decreased impedance when no power supply voltage is supplied. The rectifying diode D2 may be constructed 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 many diodes are integrated.

[Operation of the optical receiving device in FIG. 1 when power is supplied]
Various power supplies can be used for the power supply means Vcc in FIG. 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 the photodiode D1 to enter a power supply state.

At the time of power supply, the power supply means Vcc also supplies power to the coil L1 and the amplifier IC1. At this time, the open switch SW1 is closed. In this state, when an optical signal transmitted through 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. When the optical input level is high (strong), the output current increases in accordance with the optical input level. When the output current changes, the current flowing through the current-voltage conversion circuit 2 also changes. A current-voltage conversion circuit 2 converts the current output from the anode side of the photodiode D1 into a voltage. The anode-side output current of the photodiode D1 is output to the output terminal OUT2 through the anode-side transmission line AL, and the cathode-side output current is output to the output terminal OUT1 through the cathode-side transmission line KL. A current flowing through the cathode-side transmission line KL is amplified by the amplifier IC1 and output to the output terminal OUT1. Since the signals output to the output terminals OUT1 and OUT2 are FM/RF multiplexed signals, the TV receiver connected to the output terminal OUT1 outputs the RF signal, and the announcement broadcast receiver connected to the output terminal OUT2 outputs the FM signal. can receive.

[Operation of the optical receiving device in FIG. 1 when power is not supplied]
When the voltage is no longer supplied from the power supply means Vcc to the optical receiving apparatus of FIG. 1 due to a power failure of the commercial power supply or other reasons (it becomes a non-powered state), the photodiode D1 is no longer in the reverse bias state, and the open switch SW1 is closed. automatically opens. In this state, when light is input to the photodiode D1, a current corresponding to the input level of light is output from the anode of the photodiode D1. This current is applied to the anode of the rectifying diode D2 via the current-voltage conversion circuit (resistor R1)2. At this time, the rectifying diode D2 is forward-biased and the impedance decreases, and the freewheeling circuit 5 is formed by the photodiode D1, the transformer T1, the resistor R1, the capacitor C4, the rectifying diode D2, and the coil L1. The current output from the anode of the photodiode D1 returns to the cathode of the photodiode D1 through the return circuit 5. FIG.

When no power is supplied, the output transistor for controlling the voltage of the power supply circuit (not shown) of the power supply means Vcc is cut off, so the current output from the cathode of the rectifying diode D2 in FIG. Almost all of the current output from the anode of the photodiode D1 flows back to the cathode of the photodiode D1 without flowing to the power supply circuit side of the power supply means Vcc. At this time, since the opening switch SW1 is open, the current does not flow through the cathode side transmission line KL, and the current output from the anode side of the photodiode D1 flows from the secondary side terminal of the transformer T1 to the capacitor C3 of the anode side transmission line AL. output to the output terminal OUT2. Since the signal output to the output terminal OUT2 is an FM/RF multiplexed signal, the receiving device connected to the output terminal OUT2 can receive the FM signal even when power is not supplied. In this case as well, the level of the FM signal does not deteriorate even if the light illuminance becomes strong and the output current becomes large (Fig. 8: this patent).

(Second Embodiment of Optical Receiver: FIG. 2)
FIG. 2 shows a second embodiment of the optical receiver of the present invention. Its basic configuration is the same as that of FIG. 1, and further, it is provided with a coupling capacitor C5 and a short-circuit switch SW2 on the cathode side transmission line KL and outside the power supply line VL. A large capacitance (for example, 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 is automatically closed when power is not supplied.

The coupling capacitor C5 is coupled with a high-frequency signal among the electric signals output from the photodiode D1. Capacitors have the characteristic that the impedance decreases as the capacitance increases, and the impedance decreases as the frequency increases. In FIG. 2, by using a large-capacity capacitor for the coupling capacitor C5, the impedance for high frequencies becomes small, and even if the optical input level increases when no power is supplied, the photoelectrically converted FM signal (high frequency signal) is output. does not decrease (Fig. 8).

[Operation of the optical receiving device in FIG. 2 when power is supplied]
In the optical signal device of FIG. 2, when power is supplied, the open switch SW1 is closed and the short circuit switch SW2 is open. The RF signal is amplified and output to the output terminal OUT1, and can be received by a TV receiver connected to the output terminal OUT1. The current output from the anode side of the photodiode D1 flows from the secondary side of the transformer T1 to the anode-side transmission line AL, is output to the output terminal OUT2, and is transmitted to the announcement broadcast receiver connected to the output terminal OUT2 to transmit the FM signal. can receive.

[Operation of the optical receiving device in FIG. 2 when power is not supplied]
When no power is supplied, the open switch SW1 is automatically opened and the short switch SW2 is automatically closed, so that the cathode-side transmission line KL is grounded (short-circuited) through the coupling capacitor C5 and the short-circuit switch SW2. Therefore, the current output from the cathode side of the photodiode D1 does not flow through the cathode-side transmission line KL, and the current output from the anode of the photodiode D1 flows from the secondary side of the transformer T1 to the anode-side transmission line AL. is output to the output terminal OUT2. Therefore, even when power is not supplied, the FM/RF signal is output to the output terminal OUT2 without lowering in level, and the FM signal can be received by the notification broadcast receiver connected to the output terminal OUT2. In this case as well, the level of the FM signal does not deteriorate even if the light illuminance becomes strong and the output current becomes large (Fig. 8: this patent).

(Embodiment 3 of Optical Receiver: FIG. 3)
The basic configuration of the optical receiver of FIG. 3 is the same as that of FIG. 1, except that a plurality of amplifiers IC1, IC2, IC3, . . . are connected in multiple stages. The amplifier IC1 can also be an integrated circuit comprising a plurality of amplifiers IC1, IC2, IC3, . . .

[Operation of the optical receiving device in FIG. 3 when power is supplied and when power is not supplied]
Since the basic configuration of the optical receiver in FIG. 3 is the same as that in FIG. 1, the operation during feeding and non-feeding is the same as in FIG.

(Embodiment 4 of Optical Receiver: FIG. 4)
The optical receiver shown in FIG. 4 is of a common output terminal type, and the output terminal OUT1 for RF signal output and the output terminal OUT2 for FM signal output of the optical receiver shown in FIGS. terminal) OUT3, and by switching the 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. .

[Operation of the optical receiving device in FIG. 4 when power is supplied and when power is not supplied]
The basic operation of the optical receiver in FIG. 4 is the same as in the case of FIG. When the receiving device connected to the common output terminal OUT3 is a TV receiver, both the RF signal and the FM signal can be received. can be done. When no power is supplied, the open switch SW1 is open, so that no current flows through the cathode-side transmission line KL, and the current flowing through the anode-side transmission line AL is output to the common output terminal OUT3 through the switch SW3. Therefore, at least the FM signal can be received by the TV receiver or announcement broadcast receiver connected to the common output terminal OUT3.

(Embodiment 5 of Optical Receiver: FIG. 5)
The basic configuration of the optical receiver of FIG. 5 is the same as that of FIG. The difference is that a mixer 3 is used in place of the change-over switch SW3 in FIG. In this case, the mixed RF/FM electric 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.

[Operation of the optical receiving device in FIG. 5 when power is supplied and when power is not supplied]
The basic operation of the optical receiving device in FIG. 5 when power is supplied and when power is not supplied is the same as in the case of FIG. The difference is that when power is supplied, 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. A receiver can receive both RF and FM signals, and an announcement broadcast receiver can receive FM signals. When no power is supplied, the opening switch SW1 is opened, so that no current flows through the cathode-side transmission line KL, and only the anode-side transmission line AL flows. It is output to the output terminal OUT3. Therefore, at least the FM signal can be received by the TV receiver or announcement broadcast receiver connected to the common output terminal OUT3.

(Embodiment 6 of Optical Receiver: FIG. 6)
Since the photodiode D1 outputs the same current from both the cathode side and the anode side, the configuration of the cathode side transmission line KL and the configuration of the anode side transmission line AL can be interchanged. The optical receiver shown in FIG. 6 is obtained by replacing the configuration of the cathode-side transmission line KL and the anode-side transmission line AL of FIG. Specifically, an open switch SW1, an amplifier IC1, and DC blocking capacitors C2 and C3 are inserted in the transmission line AL on the anode side, and a capacitor C3 is inserted in the transmission line KL on the cathode side.

[Operation of the optical receiving device in FIG. 6 when power is supplied]
In the optical receiver of FIG. 6, since the open switch SW1 is closed during power supply, the current output from the cathode of the photodiode D1 flows through the cathode-side transmission line KL, and the current output from the anode flows into the anode-side transmission line AL. output to Electric signals flowing through the respective transmission lines KL and AL are output to output terminals OUT1 and OUT2, and receiving devices connected to the output terminals OUT1 and OUT2 can receive FM signals and RF signals.

[Operation of the optical receiving device in FIG. 6 when power is not supplied]
Since the open switch SW1 is open when power is not supplied, the current output from the anode of the photodiode D1 does not flow through the anode-side transmission line AL, but the current output from the cathode flows through the cathode-side transmission line KL. It is output to the output terminal OUT1. Therefore, even when no power is supplied, at least the receiving device connected to the output terminal OUT1 can receive the FM signal.

(Embodiment 7 of Optical Receiver: FIG. 7)
In the embodiment of FIG. 7, the configuration of the cathode-side transmission line KL and the configuration of the anode-side transmission line AL of FIG. 2 are exchanged. Specifically, a capacitor C3 is placed in the transmission line KL on the cathode side, an open switch SW1, a capacitor C1, an amplifier IC1, and a capacitor C2 are provided in the transmission line AL on the anode side, and a coupling capacitor C5 and a short-circuit switch SW2 are provided. be. The open switch SW1 is closed when power is supplied and automatically switches to open when power is not supplied, as in the case of FIG. A large-capacity capacitor is suitable for the coupling capacitor C5, as in the case of FIG.

[Operation of the optical receiving device in FIG. 7 when power is supplied]
In the optical receiver of FIG. 7, when power is supplied, the current output from the cathode of the 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. FM signals and RF signals can be received by receiving devices connected to the output terminals OUT1 and OUT2 of the AL.

[Operation of the optical receiving device in FIG. 7 when power is not supplied]
In the optical receiver of FIG. 7, the open switch SW1 is open and the short switch SW2 is closed when power is not supplied. The applied current flows through the cathode-side transmission line KL and is output to the output terminal OUT1. Therefore, the FM/RF signal is output to the output terminal OUT1, and at least the FM signal can be received by the receiving device connected to the output terminal OUT1.

Since the above-described embodiments are merely examples of the present invention, the present invention is not limited to those embodiments, and design changes are possible within the scope of solving the problems of the invention.

REFERENCE SIGNS LIST 1 photoelectric conversion means 2 current-voltage conversion circuit 3 mixer 4 opening means 5 return circuit D1 photodiode D2 rectifying diode L1, L2 coils C1, C2, C3 capacitor C5 coupling capacitor SW1 open switch SW2 short-circuit switch SW3 change-over 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 (8)

In an optical receiving method for photoelectrically converting an optical signal containing an FM signal and an RF signal into an electrical signal containing both signals by photoelectric conversion means,
When power is supplied to the photoelectric conversion means, the photoelectric conversion means converts the 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. , capable of receiving FM and/or RF signals with receiving equipment connected to the output end of each transmission line,
When no power supply is supplied to the photoelectric conversion means, the photoelectric conversion means converts the optical signal into an electric signal and outputs the signal to both of the two transmission lines connected to the two output sides of the photoelectric conversion means. However, one of the transmission lines is opened by the opening means and no electrical signal is output from that transmission line, and an electrical signal is output only from the other transmission line that is not opened and is connected to the transmission line that is not opened. The receiving device was able to receive at least FM signals,
An optical receiving method characterized by: 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. An electrical signal output from the anode side of the photodiode is output to the anode-side transmission line, and an electrical signal output from the cathode side is output to the cathode-side transmission line. At least the FM signal is output from the transmission line that is opened and the other is not opened,
An optical receiving method characterized by: In the optical receiving method according to claim 1 or claim 2,
The current output from the photoelectric conversion means is circulated to the photoelectric conversion means through the return means, which is in a reverse bias state and impedance increases when power is supplied, and is forward bias state and impedance decreases when power is not supplied. bottom,
An optical receiving method characterized by: In an optical receiver equipped with photoelectric conversion means for receiving an optical signal containing an FM signal and an RF signal and converting it into an electrical signal containing both signals,
a photoelectric conversion means for converting the optical signal into a current;
power supply means for supplying voltage to the photoelectric conversion means;
comprising two transmission lines for transmitting currents output from two output sides of the photoelectric conversion means;
one of the two transmission lines has an opening means capable of opening the transmission line;
When power is supplied from the power supply means to the photoelectric conversion means, a current is output to the two transmission lines,
When no power is supplied from the power supply means to the photoelectric conversion means, the transmission line provided with the opening means is opened by the opening means so that no current flows through the transmission line, and current only flows from 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 an open transmission line,
An optical receiver characterized by: The optical receiver according to claim 4,
the opening means comprises a switch,
An optical receiver characterized by: 6. In the optical receiver according to claim 4 or 5,
The photoelectric conversion means is a photodiode, one transmission line is an anode-side transmission line for transmitting an electric signal output from the anode side of the photodiode, and the other transmission line is an electric signal output from the cathode side of the photodiode. A cathode-side transmission line that transmits a signal,
An optical receiver characterized by: The optical receiver according to any one of claims 4 to 6,
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 receiver characterized by: The optical receiver according to claim 7,
A rectifying means connected in parallel with the photoelectric conversion means and the current-voltage conversion means,
When power is supplied from the power supply means, the rectifying means is in a reverse biased state and the impedance increases, and when power is not supplied, the rectifying means is in a forward biased state and the impedance decreases.
An optical receiver characterized by:

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