JPH0993205A - Optical receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical receiver of a totally amplifier type by which low noise at an AM band and a wide frequency characteristic at an FM band are ensured. SOLUTION: The receiver is provided with a light receiving element 1 converting an optical signal into an electric signal, an impedance matching transformer 3 to take the matching of a signal at an AM band for the light receiving element 1 and an amplifier 2, a high pass filter 4 used to take matching a signal at an FM band for them, and an amplifier 2 for signal amplification. The AM band and the FM band are totally amplified through the impedance matching. Furthermore, the impedance at the outside of the pass band of the high pass filter 4 is set sufficiently high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver capable of receiving an AM modulated signal and an FM modulated signal.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional optical receiving apparatus, in which an optically transmitted optical signal is converted into an electric signal by a light receiving element 14. Then, from the cathode of the light receiving element 14, only a low frequency band AM band signal is taken out by the low pass filter (LPF) 9, and further the amplifier 11 and the light receiving element 14 are matched by the LPF 9 and the impedance matching transformer 10. By transmitting A
Achieves low noise in the M band.

A high frequency band FM band signal is extracted from the anode of the light receiving element 14 by a high pass filter (HPF) 12 and output from an amplifier 13. Light receiving element
A wide band in the FM band is realized by matching the 14 and the amplifier 13.

Next, the operation of the conventional optical receiver will be described.

The optically transmitted optical signal is converted into an electric signal by the light receiving element 14. Then, only the AM band signal is extracted from the cathode of the light receiving element 14 by the LPF 9. As the LPF 9, an LPF having impedance matching the impedance of the light receiving element 14 and the impedance matching transformer 10 and having a low out-of-band impedance is used.

The reason why the impedance outside the band of the LPF 9 is lowered is to prevent the LPF 9 from consuming a signal to be taken out in the FM band among the signals taken out from the light receiving element 14. By performing impedance matching between the light receiving element 14 and the amplifier 11 by the LPF 9 and the impedance matching transformer 10, the light receiving element 14
It is possible to improve the transmission efficiency of the electric power that can be extracted from the.
By this operation, the noise component of the output of the amplifier 11 does not change and only the signal component increases, so that the noise in the AM band can be reduced.

The signal in the FM band is taken out from the anode of the light receiving element 14 by the HPF 12. HPF12 is the above A
For the same reason as the LPF 9 in the M band, a LPF 9 having a low out-of-band impedance is used. Light receiving element 14 and amplifier 13
Impedance matching of is done by using HPF12.
As the PF12, one having an impedance that can secure a wide band of the FM band is used.

[0008]

However, in the conventional optical receiving apparatus described above, an amplifier for separately amplifying the AM band and the FM band, that is, the amplifier 11 and the amplifier 13 is required, which increases the cost. It was the cause.

An object of the present invention is to solve the above problems of the prior art and to provide a collective amplification type optical receiver capable of reducing the number of amplifiers installed.

[0010]

In order to achieve the above object, the present invention provides a light receiving element for electrically converting an optical signal,
An optical receiving device, comprising an amplifier for amplifying the converted electric signal, capable of receiving an AM modulation signal in a low frequency region and an FM modulation signal in a high frequency region, and between the light receiving element and the amplifier. , An AM band impedance matching transformer and a FM band impedance matching high pass filter are connected in parallel and inserted.

In the optical receiver, a capacitor and a resistor are connected in series between the light receiving element and the amplifier for impedance matching in the FM band and are grounded.

[0012]

According to the optical receiver of the present invention having the above structure,
The impedance between the light receiving element and the amplifier is given a frequency characteristic to perform impedance matching, and the AM band and the FM band can be collectively amplified by the same amplifier to reduce the number of necessary amplifiers. To do.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention, in which a light receiving element 1 for converting an optical signal into an electric signal, an amplifier 2 for signal amplification, and an AM band of the light receiving element 1 and the amplifier 2 are provided. Transformer 3 for impedance matching to achieve matching
And an HPF 4 for matching the FM band.

Next, the operation of the first embodiment will be described.

By performing the impedance matching between the light receiving element 1 and the amplifier 2 by the impedance matching transformer 3, it is possible to improve the transmission efficiency of the electric power that can be extracted from the light receiving element 1. By this operation, the noise component of the output of the amplifier 2 does not change and only the signal component increases, so that the noise in the AM band can be reduced.

The light receiving element 1 has a capacitance, and due to the capacitance, high impedance, and inductance of the transformer 3 for impedance matching, when only the transformer 3 for impedance matching is used, the band extends only to the AM band. . In order to compensate for this, an HPF 4 for matching the FM band is provided in parallel with the impedance matching transformer 3, and the impedance of this HPF 4 is set lower than that of the impedance matching transformer 3 to set a wide band of the FM band. Can be secured. HP
F4 makes impedance outside the pass band sufficiently high,
The impedance outside the pass band should not reduce the impedance in the AM band.

As described above, according to the first embodiment, the impedance between the light receiving element 1 and the amplifier 2 is given a frequency characteristic for impedance matching, and the AM band and the FM band are collectively amplified. This can reduce the number of amplifiers installed.

FIG. 2 is a block diagram of a second embodiment of the present invention, which is provided with a light receiving element 5 for converting an optical signal into an electric signal and an amplifier 6 for amplifying a signal, and between the light receiving element 5 and the amplifier 6. A capacitor 7 and a resistor 8 are connected in series and grounded for impedance matching in the FM band.

Next, the operation of the second embodiment will be described.

The light receiving element 5 converts the optical signal into an electric signal. The converted electric signal is amplified by the amplifier 6 and output. Impedance matching of the light receiving element 5 and the amplifier 6 in the AM band is performed by the input impedance of the amplifier 6 to improve the transmission efficiency of electric power that can be extracted from the light receiving element 5. As a result, the noise component of the output of the amplifier 6 does not change and only the signal component becomes large.
Noise reduction in the M band can be achieved.

Since the light receiving element 5 has a high impedance, when impedance matching is performed, a low-pass filter is formed due to the capacitance of the light receiving element 5 and a high load impedance, and the band does not extend to the FM band. In order to prevent this, a transmission line between the light receiving element 5 and the amplifier 6 in which a capacitor 7 and a resistor 8 are connected in series is grounded.

Since the capacitor 7 has a high impedance in the low range, the impedance in the AM band does not decrease. When the frequency becomes high, the impedance of the capacitor 7 becomes low, and the sum of the resistance components of the resistor 8 and the capacitor 7 is grounded from the transmission line, so that the impedance of the transmission line can be lowered. By this operation, a wide band of the FM band can be secured.

As described above, according to the second embodiment, the one in which the capacitor 7 and the resistor 8 are connected in series between the light receiving element 5 and the amplifier 6 is grounded, and the impedance is given a frequency characteristic to obtain the impedance. It is possible to reduce the number of amplifiers to be installed by performing matching and amplifying the AM band and the FM band together with the same amplifier.

[0025]

As described above, according to the optical receiving apparatus of the present invention, the impedance between the light receiving element and the amplifier is given a frequency characteristic and impedance matching is performed, whereby the AM band and the FM band. Since the amplifiers can be amplified together, the number of amplifiers to be installed can be reduced, the configuration can be simplified, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of an optical receiver according to the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the optical receiving apparatus of the present invention.

FIG. 3 is a configuration diagram of a conventional optical receiver.

[Explanation of symbols]

1, 5 ... Light receiving element, 2, 6 ... Amplifier, 3 ... Transformer, 4 ... HPF (high-pass filter), 7 ... Capacitor, 8 ... Resistor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H03F 3/08

Claims (2)

[Claims] 1. A light-receiving element for electrically converting an optical signal,
An optical receiving device, comprising an amplifier for amplifying the converted electric signal, capable of receiving an AM modulation signal in a low frequency region and an FM modulation signal in a high frequency region, and between the light receiving element and the amplifier. , An optical receiving device in which a transformer for matching impedance in AM band and a high-pass filter for matching impedance in FM band are connected in parallel. 2. A light receiving element for electrically converting an optical signal,
An optical receiving device, comprising an amplifier for amplifying the converted electric signal, capable of receiving an AM modulation signal in a low frequency region and an FM modulation signal in a high frequency region, and between the light receiving element and the amplifier. , An optical receiver in which a capacitor and a resistor are connected in series to perform impedance matching in the FM band and is grounded.