JP4781953B2 - Optical receiver - Google Patents

Description

  The present invention relates to an optical receiver that converts, for example, an optical signal transmitted through an optical network into an electrical signal at a terminal of the network and outputs the electrical signal.

  An optical receiver may be used for a joint reception system using an optical network, for example. In such a joint reception system, it is necessary to be able to receive an emergency notification or the like with an optical receiver even during a power failure. A countermeasure for that is disclosed in, for example, Patent Document 1.

  In Patent Document 1, an anode of a photodiode that is a light receiving element is grounded via a current multiplication transformer. The cathode of the photodiode is connected to the positive power supply terminal through a series circuit of three resistors. In this series circuit, a backflow prevention diode is connected with its cathode as the photodiode side and its anode as the positive power supply terminal side, and a large capacity capacitor is connected between the cathode of this backflow prevention diode and the ground potential point. . When a positive voltage is supplied to the power supply terminal and the photodiode is operating, the large-capacity capacitor is charged at the same time. When a positive voltage is not supplied to the power supply terminal due to a power failure, the large-capacity capacitor is discharged and the photodiode is operated.

JP 2006-174221 A

  In this optical receiver, since the large-capacity capacitor functions as an uninterruptible power supply, the photodiode can be operated even during a power failure. However, the operating time of the photodiode from the start of the power failure is determined by the capacity of the large capacity capacitor. Accordingly, if it is necessary to operate the photodiode even after a considerable time has elapsed since the start of the power failure, the capacity of the large-capacitance capacitor must be considerably increased. A large-capacity capacitor having a large capacity becomes large, and an optical receiver itself using such a large-capacitance capacitor becomes quite large.

  It is an object of the present invention to provide an optical receiver that can be miniaturized so that an optical signal can be received even if a considerable amount of time has passed since power supply was stopped without using an uninterruptible power supply device. Objective.

  The optical receiver of one embodiment of the present invention includes a light receiving unit and a non-power receiving unit. The light receiving means converts the optical signal into an electric signal in the power supply state. The no-power light receiving means converts an optical signal into an electric signal in a power-off state. For example, a photodiode can be used as the light receiving means and the non-power receiving light receiving means. However, when used as a light receiving means, the photodiode is in a reverse bias supply state, and when used as a non-powered light receiving means, it is in a non-biased state, and a load is connected between both ends of the photodiode. . The optical signal switching means supplies the optical signal to the light receiving means in a power supply state, and supplies the optical signal to the non-power supply light receiving means in the power non-supply state. It is desirable that the optical signal switching means be mechanically switched.

  In another aspect of the present invention, a light receiving means and a non-power-receiving light receiving means are provided in the same manner as in the above aspect. These are always supplied with optical signals, each of which always generates an electrical signal. Further, the selection means selects and outputs the electric signal of the light receiving means in the power supply state, and selects and outputs the electric signal of the non-power supply light receiving means in the power non-supply state.

  In the above two aspects, since the light receiving means and the non-power-receiving light-receiving means are provided, an electrical signal is output from the light-receiving means when power is supplied, and an electrical signal is output from the non-power-receiving light means when power is not supplied. . Therefore, it is possible to receive an optical signal even if a long time has passed after the power supply is stopped, and it is not necessary to install an uninterruptible power supply, and the optical receiver can be miniaturized. Furthermore, in the above aspect, since the optical signal switching means is configured not to supply the optical signal to the non-power receiving light receiving means when the power is supplied, the electric signal of the non-power receiving light receiving means is not generated when the power is not supplied. This is not mixed with the electrical signal of the light receiving element, and the electrical signal of the non-powered light receiving means does not adversely affect the characteristics of the electrical signal of the light receiving means. In a later aspect, there is a possibility that an electric signal is also generated from the non-power receiving means when power is supplied. However, since only the electrical signal of the light receiving means is selected by the selection means, the electrical signals of the light receiving means and the non-powered light receiving means are not mixed, and the electrical signal of the non-powered light receiving means is added to the electrical signal of the light receiving means. There is no adverse effect.

  The optical receiver according to another aspect of the present invention includes light receiving means. The light receiving means converts the optical signal into an electric signal when an optical signal is supplied in a biased state or a non-biased state. As the light receiving means, for example, when receiving an optical signal, a bipolar element, for example, a photodiode, through which a current flows can be used, and a load connected between the one pole and a reference potential point can be used. it can. As the load, for example, a high-frequency transformer, a high-frequency inductor or a resistor can be used. When supplying power, the bias supply means supplies a bias to the light receiving means. For example, a bias is supplied to the other end of the bipolar element. When power is supplied, the amplifying means amplifies the electric signal from the light receiving means. The selection means selects the output signal of the amplification means when power is supplied, and selects the electrical signal of the light receiving means when power is not supplied.

  In the optical receiver of this aspect, when power is supplied, the bias is supplied to the light receiving means by the bias supplying means, the light receiving means operates in a biased state, and the electrical signal generated by the light receiving means is amplified by the amplifying means, and the selecting means Is selected and output. When the power is not supplied, the light receiving means generates an electric signal in a non-biased state, and this electric signal is selected and output by the selecting means. Even in this optical receiver, an electric signal from the light receiving means is always output when power is not supplied. And since an uninterruptible power supply is unnecessary, this optical receiver can be reduced in size.

  As described above, according to the present invention, an electrical signal obtained by converting an optical signal can be obtained even when the power supply is stopped without using an uninterruptible power supply device, An optical signal can be converted into an electrical signal even if a considerable amount of time has passed since the supply was stopped. In addition, since no uninterruptible power supply is used, the optical receiver can be downsized.

  The optical receiver according to the first embodiment of the present invention is provided in a terminal of an optical transmission line in an optical joint reception system, for example, an optical subscriber terminal device provided in each home. This optical receiver has an optical signal switching means, for example, an optical switch 4 connected to an optical transmission line, for example, an optical fiber 2. The optical switch 4 supplies an optical signal transmitted through the optical fiber 2 to one of the two optical paths 6a and 6b. The optical switch 4 is mechanically switchable, and when the optical receiver is energized, an optical signal is supplied to the optical path 6a side. However, the optical receiver is de-energized due to a power failure, for example. Is switched to the optical path 6b side.

  In the optical path 6a, a light receiving means, for example, a photoelectric conversion unit 8 is installed to convert an optical signal supplied via the optical path 6a into an electric signal, for example, a high frequency signal. The optical signal is a television signal, for example, a terrestrial television broadcast signal, a satellite broadcast intermediate frequency signal, a satellite communication intermediate frequency signal, or a high-frequency signal such as a joint reception independent broadcast signal converted into an optical signal. 8 is converted to the original television signal. The photoelectric conversion unit 8 has a known configuration including a light receiving element, for example, a photodiode (not shown), and a reverse bias voltage is supplied to the photodiode from a bias terminal 8a. The television signal output from the photoelectric conversion unit 8 is amplified by the high-frequency amplifier 10 and supplied to the combining means, for example, the combiner 12.

  For example, an optical signal supplied to the optical path 6b by the optical switch 4 at the time of a power failure is converted into a high-frequency signal by a non-power-receiving light-receiving means, for example, a non-power-supply photoelectric conversion unit 14. The non-power source photoelectric conversion unit 14 is configured as shown in FIG. 2, for example. The non-power source photoelectric conversion unit 14 includes a light receiving element, for example, a photodiode 16. The photodiode 16 receives an optical signal and generates a voltage according to the amount of light between the anode and the cathode at both ends thereof.

  The anode and the cathode of the photodiode 16 are connected between a load, for example, a transformer, specifically, a primary winding 18 p of the high-frequency transformer 18. The primary winding 18p has an intermediate tap 18t, and the intermediate tap 18t is connected to a reference potential, for example, a ground potential. The anode of the photodiode 16 is connected to the ground potential via the high frequency blocking coil 20. As a result, the anode is not grounded in terms of high frequency.

  One end of the secondary winding 18s of the high-frequency transformer 18 is grounded, and the other end is connected to the combiner 12 shown in FIG.

  In the no-power photoelectric conversion unit 14, no bias is supplied to the photodiode 16, and the photodiode 16 is used in a no-bias state. Therefore, the non-power source photoelectric conversion unit 14 can convert an optical signal into a television signal even in a power failure state.

  In the non-power-source photoelectric conversion unit 14 configured as described above, when the photodiode 16 receives an optical signal, a voltage is generated with the anode side of the photodiode 16 being positive and the cathode side being negative according to the received light level. Based on this voltage, a current flows through the primary winding 18 p of the high-frequency transformer 18, and a television signal is induced in the secondary winding 18 s, which is supplied to the combiner 12 via the capacitor 22. The output signal of the synthesizer 12 is supplied to a subsequent signal processing circuit (not shown) via an output terminal 24, demodulated, and supplied to a television receiver (not shown).

  In the optical receiver configured as described above, the optical signal transmitted through the optical fiber is supplied to the optical path 6 a by the optical switch 4 in a state where power is supplied. The optical signal in the optical path 6a is supplied to the photoelectric conversion unit 8, where it is converted into a television signal. The television signal is amplified by the amplifier 10, supplied to the output terminal 24 through the synthesizer 12, supplied from there to the processing circuit, processed by the processing circuit, and supplied to the television receiver. At this time, since no optical signal is supplied to the optical path 6b, the no-power photoelectric conversion unit 14 does not generate a television signal, and the television signal from the photoelectric conversion unit 8 and the amplifier 10 and the combiner 12 are not generated. Are not combined and do not interfere with the television signals from the photoelectric conversion unit 8 and the amplifier 10.

On the other hand, in a state where power is not supplied due to a power failure or the like, the optical signal transmitted through the optical fiber is supplied to the optical path 6b by the optical switch 4. The optical signal in the optical path 6b is supplied to the no-power photoelectric conversion unit 14, converted into a television signal even when no power is supplied, and supplied to the processing circuit via the synthesizer 12 and the output terminal 24, where Processed and supplied to the television receiver. Therefore, even if an emergency broadcast is performed by terrestrial television broadcast, satellite broadcast, satellite communication, or voluntary broadcast during a power failure, the broadcast content can be viewed. Moreover, the voltage generated in the photodiode 16, the greater the level of the optical modulation signal input to the photodiode 16, the level output from the secondary winding 36s is increased. Therefore, even when the input level of the optical modulation signal becomes high, the television signal supplied to the processing circuit can be increased, and this is effective when the maximum optical input level can be defined, and the optical input level that is normally used is 0 dBm or less. Then it can be used without problems. Further, since a power failure has occurred, a television signal is not generated from the photoelectric conversion unit 8, and even if it is generated, the amplifier 10 is not operating. Therefore, the synthesizer 12 includes the photoelectric conversion unit 8 and the amplifier 10. The television signal is not supplied, and the synthesizer 12 does not interfere with the television signal from the no-power photoelectric conversion unit 14.

  Thus, in this optical receiver, when the power supply is stopped, the photoelectric conversion unit 8 and the amplifier 10 are not operating, but the uninterruptible photoelectric conversion unit 14 is continuously operating, and the optical signal Can be converted into a television signal. Therefore, even if an uninterruptible power supply device is not used, a television signal converted from an optical signal can be obtained when the power supply is stopped, and a considerable amount of time has passed since the power failure. Even an optical signal can be converted into a television signal. In addition, since the uninterruptible power supply is not used at all, the optical receiver can be downsized.

  As shown in FIG. 3, the optical receiver according to the second embodiment of the present invention uses the same light receiving element, for example, the photodiode 26, regardless of whether power is supplied or not.

  The cathode of the photodiode 26 is connected to bias means, for example, a bias circuit 28. The bias circuit 28 includes two resistors 32 and 34 connected in series between a bias power supply terminal 30 to which a positive DC voltage is supplied and a reference potential, for example, a ground potential. The cathode of the photodiode 26 is connected to the connection point.

  The anode of the photodiode 26 is grounded via a load, for example, a series circuit of a primary winding 36p of the high-frequency transformer 36 and a resistor 38. As a result, the anode of the photodiode 26 is connected to the ground potential in terms of DC, but not connected to the ground potential in terms of high frequency.

  A television signal generated between both ends of the series circuit is amplified by amplifying means, for example, two high-frequency amplifiers 42a and 42b, via a capacitor 40, and supplied to a selecting means, for example, a contact 44a of a changeover switch 44. . A television signal induced in the secondary winding 36 s of the high-frequency transformer 36 is supplied to the contact 44 b of the changeover switch 44. The contact 44c comes into contact with either one of the contacts 44a and 44b. The high-frequency amplifiers 42a and 42b are operated by operating power supplied from a power supply unit (not shown) when power is supplied to the optical receiver. Accordingly, the high frequency amplifiers 42a and 42b do not operate when power is not supplied to the optical receiver due to a power failure or the like.

  The changeover switch 44 is constituted by, for example, a relay. When power is supplied to the optical receiver, the relay drive coil (not shown) is energized, the contact 44c comes into contact with the contact 44a, a power failure, etc. When the power is not supplied to the optical receiver and the relay drive coil is not energized, the contact 44c contacts the contact 44b. The contact 44c is connected to an output terminal 46. The output terminal 46 is connected to a processing circuit similarly to the output terminal 24 of the first embodiment, and the output of the processing circuit is supplied to a television receiver.

  Therefore, when power is supplied to the optical receiver, a reverse bias is supplied to the photodiode 26 by the bias circuit 28, and when the photodiode 26 receives the optical signal, the primary coil 36p and the resistor of the high-frequency transformer 36 are received. A television signal is generated between the units 38 and is amplified by the amplifiers 42a and 42b via the capacitor 40. At this time, since the contact 44c of the changeover switch 44 is in contact with the contact 44a, the television signal amplified by the amplifiers 44a and 44b is supplied to the output terminal 46 via the changeover switch 44.

  On the other hand, in a power failure state in which power is not supplied to the optical receiver, the cathode of the photodiode 26 is connected to the ground potential via the resistor 34, and the anode is connected to the primary coil 36 p and the resistor 38 of the high-frequency transformer 36. To the ground potential, the photodiode 26 is in a non-biased state. In this state, when the photodiode 26 receives an optical signal, a positive voltage is generated on the cathode side and a negative voltage is generated on the anode side, and a television signal is induced in the secondary coil 36 s of the high-frequency transformer 36 by the current that flows. . At this time, the contact 44 c of the changeover switch 44 contacts the contact 44 b, and a television signal is supplied to the output terminal 46 via the changeover switch 44.

  Also in the optical receiver of this embodiment, even when the power supply is stopped, the photodiode 26 can be converted into a television signal with no bias applied. Therefore, even if an uninterruptible power supply device is not used, a television signal converted from an optical signal can be obtained when the power supply is stopped, and a considerable amount of time has passed since the power failure. Even an optical signal can be converted into a television signal. Further, since no uninterruptible power supply is used, the optical receiver can be downsized. In addition, one photodiode 26 can be used in common at the time of power supply and at the time of power failure, parts can be saved, and cost can be reduced.

  A third embodiment of the present invention is shown in FIG. In this embodiment, a resistor 50 is connected to the anode of the photodiode 26 as a load. Since the resistor 50 is used as a load and the high-frequency transformer 36 is not used, it can be configured at a lower cost. The connection point between the resistor 50 and the anode of the photodiode 26 is connected to switching means, for example, a contact 52 c of the changeover switch 52. The contact 52a that can be contacted by the contact 52c is connected to the high-frequency amplifier 42a via the capacitor 40. The contact 52b with which the contact 52c can contact is connected to the contact 44b of the changeover switch 44. The changeover switch 52 is interlocked with the changeover switch 44. When the contact 44c of the changeover switch 44 is in contact with the contact 44a, the contact 52c of the changeover switch 52 is in contact with the contact 52a. Similarly, when the contact 44c of the changeover switch 44 is in contact with the contact 44b, the contact 52c of the changeover switch 52 is in contact with the contact 52b. Other configurations are the same as those of the second embodiment.

  Therefore, in the energized state where the power supply is not stopped, the reverse bias is supplied to the photodiode 26 by the bias circuit 28, and the television signal is received between the both ends of the resistor 50 by the photodiode 26 receiving the optical signal. This is amplified by the amplifiers 42 a and 42 b via the changeover switch 52 and the capacitor 40, and supplied to the output terminal 46 via the changeover switch 44. On the other hand, in a power failure state in which no power is supplied to the optical receiver, the cathode of the photodiode 26 is connected to the ground potential via the resistor 34, and the anode is connected to the ground potential via the resistor 50, The diode 26 is not biased. In this state, when the photodiode 26 receives an optical signal, a positive voltage is generated on the cathode side and a negative voltage is generated on the anode side, and a television signal is generated between both ends of the resistor 50 due to the current that flows. At this time, the contacts 44c and 52c of the changeover switches 44 and 52 come into contact with the contacts 44b and 52b, and a television signal is supplied to the output terminal 46 via the changeover switches 52 and 44.

  A fourth embodiment of the present invention is shown in FIG. In this embodiment, the cathode of the photodiode 26 is connected to switching means, for example, a contact 54 c of the changeover switch 54. The contact 54c can contact the contact 54a connected to the connection point of the resistors 32 and 34 of the bias circuit 28, and can contact the grounded contact 54b. The changeover switch 54 is interlocked with the changeover switches 44 and 52. When the contacts 44c and 52c of the changeover switches 44 and 52 are in contact with the contacts 44a and 52a, the contact 54c of the changeover switch 54 becomes the contact 54a. Contact. Similarly, when the contacts 44c and 52c of the changeover switches 44 and 52 are in contact with the contacts 44b and 52b, the contact 54c of the changeover switch 54 is in contact with the contact 54b. Other configurations are the same as those of the third embodiment.

  Accordingly, in the energized state where the power supply is not stopped, the reverse bias is supplied to the photodiode 26 by the bias circuit 28 via the changeover switch 54, and both ends of the resistor 50 are received by the photodiode 26 receiving the optical signal. A television signal is generated in the meantime, which is amplified by the amplifiers 42 a and 42 b via the changeover switch 52 and the capacitor 40, and supplied to the output terminal 46 via the changeover switch 44. On the other hand, in a power failure state in which power is not supplied to the optical receiver, the cathode of the photodiode 26 is connected to the ground potential via the changeover switch 54, and the anode is connected to the ground potential via the resistor 50. The diode 26 is not biased. In this state, when the photodiode 26 receives an optical signal, a positive voltage is generated on the cathode side and a negative voltage is generated on the anode side, and a television signal is generated between both ends of the resistor 50 due to the current that flows. At this time, the contacts 44c and 52c of the changeover switches 44 and 52 come into contact with the contacts 44b and 52b, and a television signal is supplied to the output terminal 46 via the changeover switches 52 and 44.

  In the above four embodiments, the optical receiver of the present invention is implemented in the subscriber terminal device of the optical joint reception system. However, the present invention is not limited to this. For example, the optical receiver is used as an optical receiver of a terminal device in the FTTH network. You can also In the no-power photoelectric conversion unit 14 of the first embodiment, the primary winding of the high-frequency transformer is connected between both ends of the photodiode 16, but instead, for example, two resistors connected in series are used. can do. In this case, the interconnection point of the resistors is connected to the ground potential, and a television signal is taken out as an output from the cathode side or the anode side of the photodiode 16. In the first embodiment, the optical signal to be supplied to the photoelectric conversion unit 8 and the non-power photoelectric conversion unit 14 is switched by the optical switch 4, but the optical signal is always sent to the photoelectric conversion unit 8 and the non-power photoelectric conversion unit 14. In place of the synthesizer 12, it is also possible to provide a selector switch that selects the output signal of the amplifier 10 when power is supplied and selects the output signal of the no-power photoelectric conversion unit 14 when a power failure occurs. In the third and fourth embodiments, the resistor 50 is used as the load of the photodiode 26. Instead of this, a high frequency coil with a tap is provided, an output is taken out from the tap, and the changeover switch 52 is used. It can also be supplied to the contact 52c.

It is a block diagram of the optical receiver of the 1st Embodiment of this invention. FIG. 2 is a circuit diagram of a non-power photoelectric conversion unit of the optical receiver of FIG. 1. It is a circuit diagram of the optical receiver of the 2nd Embodiment of this invention. It is a circuit diagram of the optical receiver of the 3rd Embodiment of this invention. It is a circuit diagram of the optical receiver of the 4th Embodiment of this invention.

Explanation of symbols

2 Optical fiber 4 Optical switch (Optical signal switching means)
8 Photoelectric converter (light receiving means)
14 No-power photoelectric conversion part (No-power light receiving means)

Claims (3)

A light receiving means for converting an optical signal into an electric signal in a power supply state;
In a non-power supply state, a non-power receiving means for converting an optical signal into an electrical signal,
An optical signal switching means for supplying the optical signal to the light receiving means in the power supply state and for supplying the optical signal to the non-power light receiving means in the power non-supply state;
Optical receiver provided. A light receiving means for converting an optical signal into an electric signal in a power supply state;
In a non-power supply state, a non-power receiving means for converting an optical signal into an electrical signal,
A selection means for selecting and outputting the electrical signal of the light receiving means in the power supply state; and a selection means for selecting and outputting the electrical signal of the non-power reception means in the power non-supply state.
Optical receiver provided. A light receiving element that converts the optical signal into an electric signal when an optical signal is supplied in a biased state or an unbiased state;
Bias means for supplying a bias to the light receiving means when power is supplied;
Amplifying means for amplifying an electrical signal from the light receiving means when the power is supplied;
A selection means for selecting an output signal of the amplifying means when the power is supplied, and an electric signal for the light receiving means when the power is not supplied;
Optical receiver provided.

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