JP2023006699A - 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 (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

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 K side of the photodiode 2 and grounded. The coupling capacitor C2 is high-frequency signal passing means for coupling and passing only high-frequency signals out of the electric signals output from the photodiode 2, so that it has high impedance in low frequencies and low impedance in high frequencies. 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 to the high-frequency signal 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.

A feature of the optical receiving method of the present invention is that, when a voltage is supplied from the power supply means to the photoelectric conversion means, the electrical signals photoelectrically converted by the photoelectric conversion means flow through both transmission lines on the output side of the photoelectric conversion means. Therefore, the receiving device connected to both transmission lines can receive the electric signal, and when no voltage is supplied from the power supply means, one of the transmission lines is short-circuited with a short-circuit having a coupling capacitor and a short-circuit switch. Then, the photoelectric conversion means is short-circuited, and the electric signal output from the photoelectric conversion means is not transmitted to the short-circuited transmission line, is transmitted to the non-short-circuited transmission line, and is connected to the receiving device connected to the transmission line. At least it should be able to receive FM signals.

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, and a short circuit that short-circuits one of the transmission lines from the photoelectric conversion means, and an electric signal on both transmission lines when power is supplied from the power supply means to the photoelectric conversion means. A transmission line having a short circuit is provided in a non-power-supply state when no power supply voltage is supplied from the power supply means to the photoelectric conversion means. The electrical signal shorted by the short circuit and output from one output side of the photoelectric conversion means is not transmitted through the transmission line, and the electrical signal output from the other output side of the photoelectric conversion means does not have a short circuit. The object is to enable at least the FM signal to be received by a receiving device connected to the transmission line transmitted through the transmission line.

It is desirable to use a capacitor with a large capacity rather than a few pF as the coupling capacitor. A photodiode can be used as the photoelectric conversion means, and an anode-side transmission line can be provided on the anode side of the photodiode, and a cathode-side transmission line can be provided on the cathode side of the photodiode.

The optical receiving method and optical receiving apparatus of the present invention have the following effects.
(1) When no power is supplied, the transmission line on one output side of the photoelectric conversion means is short-circuited by a short circuit and is short-circuited from the photoelectric conversion means. flow to the other transmission line that is not shorted. For this reason, even if the input level of the optical signal increases 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.
(2) Since a large-capacity capacitor can be used as a coupling capacitor, the impedance for high-frequency signals 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).

FIG. 4 is a circuit diagram showing an example of the optical receiver according to the present invention, in which a short circuit (coupling capacitor and short circuit 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 outside the power supply line; 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. 12 is a circuit diagram of another example of the optical receiver of the present invention, in which the output terminal is one output terminal (common output terminal) and two transmission lines are switched and connected to the common terminal by a switch. 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 to the common output terminal by a mixer; 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 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.

Embodiments of an optical receiving method and an optical receiving apparatus according to the present invention will be described together below.
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 photoelectrically converted electrical signals are transmitted through both of the two transmission lines on the output side of the photoelectric conversion means, An electrical signal can be received by a receiving device connected to the transmission line, and when no power is supplied, one of the transmission lines is shorted with a short circuit, and the electrical signal output from the photoelectric conversion means is transmitted from the shorted transmission line. is not output, and is output only from a transmission line that is not short-circuited, so that at least FM electric signals can be received by a receiving device connected to the transmission line.

(Embodiment 1 of Optical Receiver: FIG. 1)
FIG. 1 shows an embodiment of the optical receiver of the present invention. This optical receiver includes photoelectric conversion means 1 for converting an optical signal into an electrical signal, power supply means Vcc for supplying power to the photoelectric conversion means 1, A current-voltage conversion means (current-voltage conversion circuit) 2 for converting the current photoelectrically converted by the photoelectric conversion means 1 into a voltage, transmission lines AL and KL provided on the two output sides of the photoelectric conversion means 1, and a rectifying diode D2. , a coil L1. One of the two transmission lines AL and KL has a short circuit 4 . The short-circuit 4 is composed of a coupling capacitor C5 and a short-circuit switch SW2, and short-circuits the transmission line KL to short-circuit the photoelectric conversion means 1 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 its anode side grounded through the current-voltage conversion circuit 2 and its cathode side connected to the power supply means Vcc and the coils L1 and L2. A return circuit 5 is configured to return to the cathode of D1.

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

Two transmission lines AL and KL shown in FIG. 1 transmit electrical signals photoelectrically converted by the photoelectric conversion means 1 to 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.

The coupling capacitor C5 is coupled with a high frequency signal out of the electrical signal output from the photodiode D1. As the coupling capacitor C5, a capacitor with a large capacitance of several tens of pF or more is suitable instead of several pF. Capacitors have the characteristic that the impedance decreases as the capacitance increases. In the present invention, by using a large-capacity capacitor for the coupling capacitor C5, the impedance for high-frequency signals becomes small, and even if the optical input level increases when no power is supplied, the photoelectrically converted FM signal (high-frequency signal) No power reduction (Fig. 8).

The short-circuit switch SW2 constitutes the short-circuit 4 in combination with the coupling capacitor C5. The short-circuit switch SW2 is provided 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 opened when power is supplied, and is automatically closed 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 open when power is supplied, is output to the output terminal OUT1, and when closed when no power is supplied, the cathode-side transmission line KL is grounded (short-circuited) and coupled. The electrical signal coupled by the capacitor C5 is grounded (short-circuited) and is not output to the output terminal OUT1.

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 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 short-circuit switch SW2 is open. 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 not supplied from the power supply means Vcc to the optical receiver of FIG. 1 due to a power failure or other reasons, the photodiode D1 is no longer in the reverse bias state, and the short-circuit switch SW2 is automatically closed. Close to 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 from the resistor R1 of the current-voltage conversion circuit 2 to the anode of the rectifying diode D2 via the transformer T1 and the coil L1. At this time, the rectifying diode D2 is forward-biased and its impedance decreases, and a closed circuit (freewheeling circuit) 5 is formed by the photodiode D1, transformer T1, resistor R1, capacitor C4, rectifying diode D2, and coil L1. Therefore, 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 short-circuit switch SW2 is closed, the circulated current is grounded (short-circuited) through the coupling capacitor C5 and the 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 from the output terminal (secondary side terminal) of the transformer T1 to the output terminal OUT2 via the coupling capacitor C3 of the anode side transmission line AL. Since the signal output to the output terminal OUT2 is an FM/RF multiplexed signal, the announcement broadcast receiver connected to the output terminal OUT2 can receive the FM signal even when no power is supplied.

(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, except that the coupling capacitor C5 and the short-circuit switch SW2 of the cathode-side transmission line KL in FIG. 2 are arranged outside the power supply line VL. A large-capacity capacitor is suitable for the coupling capacitor C5, as in the case of FIG. As in the case of FIG. 1, the short-circuit switch SW2 is also open when power is supplied, and is automatically switched to closed when power is not supplied.

[Operation of the optical receiving device in FIG. 2 when power is supplied]
The operation of the optical signal device in FIG. 2 when power is supplied and the operation when power is not supplied are the same as in the case of FIG. That is, since the short-circuit switch SW2 is open during power supply, the current that is output from the cathode side of the photodiode D1 and flows through the cathode-side transmission line KL is amplified by the amplifier IC1 and output to the output terminal OUT1, and then to the output terminal OUT1. A connected TV receiver can receive the RF signal. 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 power is not supplied, the short-circuit switch SW2 is automatically closed, and 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 is not output to the cathode-side transmission line KL, but 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, so that the announcement broadcast receiver connected to the output terminal OUT2 can receive the FM signal.

(Embodiment 3 of Optical Receiver: FIG. 3)
The optical receiving apparatus in FIG. 1 uses only one amplifier IC1, but FIG. 3 uses a plurality of amplifiers IC1, IC2, IC3, . . . 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]
The optical receiver of FIG. 3 has the same basic configuration as that of FIG. 1, except that the amplifier IC1 is plural. The operation of is the same as in the case of 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. ) 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. The operation up to the changeover switch SW3 during power feeding and non-feeding of the optical receiver of FIG. 4 is the same as in the case of FIGS. Therefore, if the receiver connected to the common output terminal OUT3 is a TV receiver, it can receive both the RF signal and the FM signal, and if it is an announcement broadcast receiver, it can receive the FM signal. .

(Embodiment 5 of Optical Receiver: FIG. 5)
The optical receiver of FIG. 5 uses a mixer 3 in place of the switch SW3 of FIG. 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 a mixed RF/FM electrical signal is output to the common output terminal OUT3. The operation up to the changeover switch SW3 when power is supplied to the optical receiver of FIG. 5 and when power is not supplied is the same as in the case of FIG. Therefore, if the receiver connected to the common output terminal OUT3 is a TV receiver, it can receive both the RF signal and the FM signal, and if it is an announcement broadcast receiver, it can receive the FM signal. .

(Embodiment 6 of Optical Receiver: FIG. 6)
In the embodiment of FIGS. 1 and 2, the cathode-side transmission line KL includes the coupling capacitor C5, the amplifier IC1, the DC blocking capacitors C2 and C3, and the like. Since the same current is output from , 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, a coupling capacitor C5, a short-circuit switch SW2, a capacitor C1, an amplifier IC1, and a capacitor C2 are provided on the transmission line AL on the anode side, and a capacitor C3 is provided on the transmission line KL on the cathode side. As in the case of FIG. 3, the short-circuit switch SW2 is opened when power is supplied and is automatically closed when power is not supplied. 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. 6 when power is supplied]
The operation of the optical receiver in FIG. 6 during power feeding is the same as in the case of FIG. A current photoelectrically converted by the 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. Electric signals flowing through the respective transmission lines 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]
The operation of the optical receiving device in FIG. 6 when power is not supplied is the same as the operation of the optical receiving device in FIG. 1 when power is not supplied. When no power is supplied, the short-circuit switch SW2 is closed and the anode-side transmission line AL is short-circuited. Therefore, the current photoelectrically converted by the photodiode D1 flows through the anode-side transmission line AL including the coupling capacitor C5 and the short-circuit switch SW2. Instead, it flows only through the cathode-side transmission line KL and is output to the output terminal OUT1. Therefore, at least the FM signal can be received by the notification broadcast receiver connected to the output terminal OUT1.

(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 coupling capacitor C5, a short-circuit switch SW2, a capacitor C1, an amplifier IC1, and a capacitor C2 are provided on the transmission line AL on the anode side, and a capacitor C3 is provided on the transmission line KL on the cathode side. As in the case of FIG. 2, the short-circuit switch SW2 is opened when power is supplied and is automatically closed when power is not supplied. 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]
The operation of the optical receiver in FIG. 7 during power feeding is the same as in the case of FIG. The current photoelectrically converted by the 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/RF signals are output to output terminals OUT1 and OUT2 connected to the respective transmission lines. The FM signal and the RF signal can be received by receiving equipment connected to the respective output terminals OUT1 and OUT2.

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

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.

1 photoelectric conversion means 2 current voltage conversion circuit 3 mixer 4 short circuit 5 return circuit D1 photodiode D2 rectifying diode L1, L2 coil C1, C2, C3 capacitor C5 coupling capacitor SW2 short circuit switch SW3 changeover 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 transmission line is shorted by a short circuit 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 shorted and connected to the transmission line that is not shorted. 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 electrical signal is output from the transmission line that is shorted and the other is not shorted,
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;
There is a short circuit in either one of the two transmission lines,
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 having the short circuit is short-circuited by the short circuit and current does not flow through the transmission line, and current flows only from 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 an unshorted transmission line,
An optical receiver characterized by: The optical receiver according to claim 4,
the short circuit consists of a combination of a coupling capacitor and a shorting 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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