JPH07264139A - Optical receiver and repeater provided with the optical receiver - Google Patents

Abstract

PURPOSE:To automatically control the gain by providing a gain control signal by which a high frequency output signal reaches a specified level with respect to a detected current obtained from a current detector to a variable gain amplifier. CONSTITUTION:The optical receiver 8 is provided with a current detector 5 detecting a current of an O/E converter 3 and a control circuit 6 controlling a gain of a variable gain amplifier 4 based on the detected current. When a photo diode is employed for the converter 3, a current flowing to the photo diode changes linearly with respect to a change in an optical input level. That is, a DC current of the converter 3 corresponding to the level of an input light received through an optical cable 16 is detected by the detector 5. The circuit 6 uses an A/D converter to convert the detected current into a digital value and estimates a loss of the optical cable based on a reference DC current and a gain control signal is given to the amplifier 4 so that an output RF signal voltage of the amplifier 4 reaches a predetermined specified voltage to change its amplification factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving device used for optical analog communication, and more particularly to an optical receiving device used for a repeater provided as a measure against dead zones of a radio calling system.

[0002]

2. Description of the Related Art A radio paging system is composed of a central base station connected to a telephone network, a plurality of peripheral base stations which are connected to the central base station by an interoffice communication line and are distributed, and a large number of radio paging receivers. Has been done. When the telephone number of the radio paging receiver is dialed from the telephone, a radio wave is transmitted from a base station in the vicinity of the service area and the corresponding paging receiver is called. In order to further improve the service of such a radio calling system, a relay device is installed in a dead zone where radio waves do not reach, such as in a premises, an underground mall, or a tunnel, and radio waves from surrounding base stations are relayed and amplified even in a dead zone. You can now receive.

FIG. 2 is a block diagram of a relay device 12 to which the present invention is applied. In the figure, 11 is a peripheral base station, 13 is a wireless unit, 14 is an electric / optical converter (E / O) that converts an electric signal into light, 15 is a distributor, 16 is an optical cable, 17 is a plurality of slave stations, Reference numeral 18 is an optical / electrical converter (O / E) that converts light into an electric signal, 19 is a combiner, and 20 is a master station. As shown in the figure, the relay device 12 is composed of a master station 20, a plurality of slave stations 17-1 to 17-n, and a cable 16 connecting them. The wireless unit 13 is the peripheral base station 1
1 receives the radio wave and outputs an amplified high frequency signal (RF signal). The RF signal output from the wireless unit 13 is converted into light by the E / O converter 14 and distributed to the plurality of slave stations 17 by the distributor 15. The plural slave stations 17 are
Since the entire area of the dead zone, underground mall, and tunnel is used as the service area, they are distributed in the range of 1 m to 20 km, for example. A low loss (0.3 dB / km to 0.5 dB / k) is applied to the connection between the plurality of slave stations 17 and the master station 20.
The optical cable 16 having the characteristics of m) is used and optical analog transmission is adopted.

Similarly, a monitoring optical signal is sent from a plurality of slave stations 17 to the master station 20 by an optical cable, converted into an electric signal by an optical / electrical converter (O / E) 18, and combined by a combiner 19. , Is input to the wireless unit 13.

FIG. 3 is a conventional block diagram of the downlink from the parent station 20 to the child station 17 in FIG.
The RF signal input 2 received by is an amplifier in the wireless unit 13. Reference numeral 14 is an E / O converter, 16 is an optical cable, and the distributor 15 is omitted. Reference numeral 9 denotes an optical receiving device in the slave station, which includes an optical / electrical converter (O / E) 3 for converting light into an electric signal and a variable gain amplifier 4. An antenna is connected to the output terminal 7 and radio waves (output RF signal) are sent to the radio paging receiver. The variable gain amplifier 4 is configured to adjust the gain when the slave station is installed to obtain a specified transmission RF output.

[0006]

In the case of a long and narrow area such as in a tunnel, the plurality of slave stations 17 provided with the optical receiver 9 are arranged so that their service areas are sequentially linked from a position close to the master station 20. Distributed in a long distance, in the case of a large area such as an underground mall, it is distributed in a vertical and horizontal grid pattern.
In any case, the lengths of the plurality of optical cables 16 connecting the master station 20 and each of the plurality of slave stations 17 are different from each other, and they are arranged at the farthest position by 1 to several meters from the closely arranged slave stations. It may reach up to 20 km with a slave station. As described above, the optical cable is characterized by low loss, but since it has a loss of 0.3 to 0.5 dB / km, it is necessary to install such a repeater 12 depending on the position of the slave station. Difference of 0 to 10 dB, and an electric signal has a difference of 0 to 20 dB, which is twice the optical loss. On the other hand, regarding the output RF signal level output to the output terminal 7 of the optical receiving device 9, in a system such as CATV in which a reproduced image is obtained by an image receiver directly connected to the output terminal 7, there is no problem even if the output level is slightly different. Although it does not occur, in a radio paging system that transmits an electric wave by connecting an antenna, the arrival range of the electric wave is different and the service range is different for each slave station, which causes a problem. The service areas of the slave stations are set to be substantially equal to each other. When the slave stations are installed, the variable gain amplifier of the optical receiver 9 is used to compensate the difference in the loss of the optical cable and to make the transmission levels substantially equal. Installation is performed by manually adjusting the gain of 4.

FIG. 4 is a characteristic example diagram of an optical RF output with respect to an input RF signal when a light emitting diode is used as the E / O converter 14, and is a diagram showing the relationship between the current and the optical output of the light emitting diode. It is shown that when a high frequency signal (input RF) is superimposed on the bias current of the light emitting diode and driven, an optical output of analog intensity modulation is obtained. Input RF
When the modulation factor of the signal is m, the optical output is A (1 + msin
pt) cos ωt, and dB when this output is demodulated
The conversion is 2 × 10 log A + 20 log m [dB].
The first term of this equation, 10 log A [dB], is a light level.

FIG. 5 is an explanatory diagram of the characteristics of the photodiode and the detection operation, and is an explanatory diagram of the demodulation (detection) operation when the photodiode is used for the O / E converter 3 of the optical receiver 9 of FIG. Optical input A from the optical cable 16 to the photodiode
Is input, B flows as the current of the photodiode.
When the optical input A is intensity-modulated by the RF signal a, the RF signal b is superimposed on the photodiode current B and output. When the optical input is level A and the modulation factor of the RF signal a is m, detection R
The F current is b. However, when the length of the optical cable 16 is long and the loss increases and the optical input A becomes A ′, the modulation degree m is constant, so that the photodiode current B ′ becomes small and the detection RF current becomes b ′. Get smaller.
The variable gain amplifier 4 needs to correct the amount by which the RF detection signal b is reduced to b ', that is, twice the loss of the optical cable whose optical input A becomes A'.

As described above, when the slave station 17 provided with the conventional optical receiver 9 is newly installed or added, the variable gain amplifier 4 needs to be manually adjusted. Therefore, the measuring instrument is transported to the site for measurement. ， There is a drawback that it takes time and labor to make adjustments.

An object of the present invention is to provide an optical receiving device capable of obtaining a high frequency output signal of a prescribed level without manually adjusting the amplification degree when the level of the received input light changes, and further, to provide a radio call. To provide a relay device in which labor and work time required for installation and adjustment are remarkably shortened by automatically compensating for a difference in loss of optical cables depending on installation positions when a plurality of slave stations of a relay device in a system are dispersedly arranged. is there.

[0011]

The optical receiving device of the present invention comprises:
An optical / electrical converter that receives a constant-level optical output on which a high-frequency signal is superimposed via an optical cable of an unspecified length and converts it into a high-frequency signal, and an output of the optical / electrical converter that amplifies the output to a specified level. And a variable gain amplifier for outputting a high frequency output signal of the optical / electrical converter, the optical / electrical converter that linearly changes in response to a level change of received light of an unspecified level A current detector for detecting a current value of an electric converter, and a control circuit for giving a gain control signal to the variable gain amplifier so that the high frequency output signal becomes a specified level with respect to a detected current value obtained from the current detector. And a loss proportional to the length of the optical cable is compensated so that the high-frequency output signal becomes the specified level regardless of the length of the optical cable.

Further, the relay apparatus of the present invention is a parent device which receives radio waves from peripheral base stations in a radio calling system, superimposes a high frequency signal of the radio waves on light of a certain level, and sends out a plurality of optical outputs from a distributor. Station, a plurality of optical cables connected to the distributor of the master station and transmitting the plurality of optical outputs, respectively, and a plurality of optical cables connected to the plurality of optical cables and distributedly arranged, and optical outputs from the master station via the respective optical cables An optical receiver for receiving a high frequency signal extracted by an optical / electrical converter and amplifying a high frequency output signal of a specified level by amplifying it with a variable gain amplifier, and an antenna for transmitting the high frequency output signal of the optical receiver are provided. In a relay device including a plurality of slave stations, a current detector for detecting a current value of the optical / electrical converter is provided in each of the optical receivers of the plurality of slave stations. A control circuit for providing the variable gain amplifier with a gain control signal such that the high frequency output signal becomes a specified level with respect to the obtained detected current value, and the length of an optical cable connected between the master station and the slave station. Regardless of this, the high frequency output signals transmitted from the antennas of the plurality of slave stations are configured to have the specified level.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. The difference from the conventional configuration is that a current detector 5 for detecting the current value of an O / E converter 3 and a detected current value thereof are used. The control circuit 6 for controlling the gain of the variable gain amplifier 4 is provided. When a photodiode is used as the O / E converter 3, the current flowing through the photodiode changes linearly with the change in the optical input level, as shown in FIG. That is, the O / E corresponding to the level of the input light received from the master station 20 of the repeater 12 via the optical cable 16.
The DC current value of the converter 3 is detected by the current detector 5. The control circuit 6, for example, converts the detected current into a digital value with an A / D converter, estimates the loss of the optical cable from the direct current value of the reference value (optical cable 0 m), and outputs the output from the output terminal 7 of the variable gain amplifier 4. The gain control signal is applied to the variable gain amplifier 4 so that the RF signal voltage becomes a predetermined specified value, and the amplification degree is changed.

[0014]

As described in detail above, by implementing the optical receiving apparatus of the present invention, the gain is automatically controlled even if the level of the input light modulated by the RF signal changes, and the specified level is obtained. The RF output signal of is obtained. Further, by providing the optical receiving device 8 of the present invention to each of a plurality of slave stations of the relay device in the radio paging system, the output transmitted from the antennas of the plurality of slave stations distributed by the optical cables 16 having different lengths. The RF signal levels can all be made approximately equal automatically. Therefore, the gain variable range of the variable gain amplifier should be set based on the distance from the installation point of the master station to the installation point of the furthest slave station due to the size of the dead area where the repeater is installed and the planar shape. Therefore, the labor and time for installation and adjustment at the time of new installation or expansion can be greatly reduced, and the practical effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a system configuration example to which the present invention is applied.

FIG. 3 is a diagram showing a configuration example of a conventional device.

FIG. 4 is an electric / optical conversion characteristic example diagram.

FIG. 5 is a diagram illustrating an example of optical / electrical conversion characteristics and an operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 RF input 2 Amplifier 3 O / E converter 4 Variable gain amplifier 5 Current detector 6 Control circuit 7 RF output terminal 8, 9 Optical receiving device 11 Peripheral base station 12 Relay device 13 Radio section 14 E / O converter 15 Distribution Device 16 Optical cable 17 Slave station 18 O / E converter 19 Combiner 20 Master station

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04B 10/14 10/06 10/04 H04B 9/00 S (72) Inventor Takashi Yokote Nakano, Tokyo 3-14-20 Higashi-Nakano, Kokusai Electric Co., Ltd. (72) Inventor Hiroshi Suzuki 3-14-20, Higashi-Nakano, Nakano-ku, Tokyo (72) Inventor Jun Suganuma 2-c, Toranomon, Minato-ku, Tokyo No. 10 No. 1 NTT Mobile Communication Network Co., Ltd.

Claims (4)

[Claims] 1. An optical / electrical converter for receiving a constant-level optical output on which a high-frequency signal is superimposed via an optical cable of an unspecified length and converting it into a high-frequency signal, and an output of the optical / electrical converter. In an optical receiving device including a variable gain amplifier that amplifies and outputs a high frequency output signal of a specified level, linearly corresponding to a level change of an unspecified level of received light input to the optical / electrical converter. A current detector that detects a changing current value of the optical / electrical converter, and a gain control signal that causes the high-frequency output signal to have a specified level with respect to the detected current value obtained from the current detector. And a control circuit for giving to an amplifier, the loss proportional to the length of the optical cable is compensated, and the high frequency output signal is set to the specified level regardless of the length of the optical cable. The optical receiver. 2. The length of the optical cable is from 1 m to 20 km.
The optical receiving device according to claim 1, wherein the optical receiving device is in any one of the following ranges. 3. A master station which receives radio waves from peripheral base stations in a radio calling system, superimposes a high frequency signal of the radio waves on light of a certain level, and sends out a plurality of optical outputs from a distributor.
A plurality of optical cables connected to the distributor of the master station and transmitting the plurality of optical outputs, respectively, and a plurality of optical cables connected to the plurality of optical cables and arranged in a distributed manner, each of which receives the optical output from the master station via the optical cable. An optical receiving device for amplifying a high frequency signal extracted by an optical / electrical converter by a variable gain amplifier to output a high frequency output signal of a specified level, and a plurality of children provided with an antenna for transmitting the high frequency output signal of the optical receiving device. In a relay device including a station, in each of the optical receivers of the plurality of slave stations, a current detector that detects a current value of the optical / electrical converter, and a detected current value obtained from the current detector. On the other hand, a control circuit for providing the variable gain amplifier with a gain control signal such that the high frequency output signal has a specified level, and a length of an optical cable connected between the master station and the slave station. Ikagani though relay apparatus high-frequency output signal transmitted from the antenna of the plurality of slave stations, characterized by being configured such that the prescribed level. 4. The repeater according to claim 3, wherein the plurality of optical cables according to claim 3 have a length in a range of 1 m to 20 km.