JP2002237783A - Repeater using optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repeater to automatically compensate difference of optical loss due to difference of length of an optical cable connected between a master machine 3 opposed to a radio base station of the repeater mounted in an underground shopping area and a tunnel as a measure against a dead band and a slave machine 4 dispersedly arranged in the underground shopping area, etc., and opposed to a portable machine. SOLUTION: Current detectors 35, 44 to detect current values of O/E converters 34, 42 to convert received light into an electric signal are provided to both of the master machine 3 and the slave machine 4. The repeater is constituted so that the difference of the loss in the optical cable is compensated by providing gain control signals by which an output RF signal level transmitted to the portable machine corresponding to the detected current values becomes a stipulated value from control circuits 37, 45 to variable gain amplifiers 36, 46 respectively. A setting adjustment work in the case of new installation of the repeater and expansion of the slave machine becomes extremely easy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repeater provided as a countermeasure for blind spots in portable telephones and automobile telephone systems, and more particularly to a repeater utilizing optical analog transmission.

[0002]

2. Description of the Related Art For example, a portable telephone system comprises an exchange connected to a telephone network, a plurality of radio base stations connected to the exchange via inter-office communication lines, and a large number of portable telephones. ing. When the calling number of the mobile phone is dialed from the telephone, a radio wave is transmitted from the wireless base station in the service area, and the corresponding mobile phone is called, and the user can talk with each other. In order to further improve the services of such mobile phone systems, repeaters are installed in blind zones where radio waves do not reach, such as in premises, underground malls, and tunnels, and radio waves from wireless base stations are relay-amplified and used in blind zones. It has become possible to communicate with mobile phones (mobile devices).

FIG. 2 is a block diagram of a relay apparatus 2 to which the present invention is applied. In the figure, 1 is a radio base station,
31 is a wireless unit, 32 is an electric / optical converter (E / O) for converting an electric signal into light, 33 is a distributor, 5 is an optical cable,
Denotes a plurality of slave units, 34 denotes an optical / electrical converter (O / E) for converting light into an electric signal, 40 denotes a combiner, and 3 denotes a master unit. 6
-1 to 6-n are wireless zones. As shown in the figure,
The relay device 2 includes a master unit 3, a plurality of slave units 4-1 to 4-n, and an optical cable 5 connecting between the slave units 4-1 to 4-n. Radio unit 3
1 receives a radio wave from the wireless base station 1 and outputs an amplified high-frequency signal (RF signal). The RF signal output from the wireless unit 31 is converted into light whose intensity is modulated by an E / O converter 32 using a light emitting diode such as a semiconductor laser diode, and is distributed to a plurality of slave units 4 by a distributor 33. You. The plurality of slave units 4 are arranged in respective zones 6-1 to 6-1.
According to 6-n, the entire area, such as the premises of a blind zone, an underground shopping mall, or a tunnel, is set as a service area.
They are distributed over a range of up to 20 km. The connection between the plurality of slave units 4 and the master unit 3 has a low loss (0.3 dB / km).
〜0.5 dB / km), and optical analog transmission is employed.

The plurality of slave units 4 are provided with an O / E converter for directly detecting the intensity-modulated light, and a radio unit for amplifying an output RF signal and transmitting the amplified RF signal from an antenna. A transmission wave from a mobile unit (mobile phone) in the wireless zone 6 of the slave unit 4 is received and amplified by the wireless unit via the antenna of the slave unit 4, and is intensity-modulated by the E / O converter similarly to the master unit. The light is converted to light and sent from the slave unit 4 to the master unit 3 together with the monitoring data via the cable 5 and is converted into an optical / electrical converter (O / E).
The signal is converted into an electric signal by 34, synthesized by the synthesizer 40, and input to the radio unit 31.

FIG. 3 is a conventional block diagram of a two-way communication line between the main unit 3 of FIG. 2 and one of the sub units 4 as a representative. The main unit 3 is the same as that of FIG. Specific examples are shown. 41 in the slave unit 4 is a wireless unit, 42 is an O / E converter,
43 is an E / O converter and 46 is a variable gain amplifier. The antenna connected to the duplexer is a shared antenna for transmitting and receiving to and from a portable device moving in the zone. Variable gain amplifier 46
Is configured such that a specified transmission RF output can be obtained by adjusting a difference in line gain due to a difference in length of the optical cable 5 when the slave unit 4 is installed.

[0006]

In a long area such as in a tunnel, a plurality of slave units 4 in the above conventional system are sequentially arranged in a zone 6 from a position close to the master unit 3.
Are scattered so as to be linked to each other, and in the case of a large area such as an underground mall, they are scattered and arranged in a vertical and horizontal lattice. In each case, the lengths of the plurality of optical cables 5 connecting the master unit 3 and each of the plurality of slave units 4 are different from each other, and the length of the plurality of optical cables 5 is one to several meters from the slave unit arranged in the vicinity, and is located at the farthest position. The slave unit may be as long as 20 km. As described above, the optical cable is characterized by a low loss.
Since there is a loss of 0.5 dB / km, the difference in the loss of the optical cable depending on the position of the slave unit is 0 to 10 dB for installing such a relay device 2, and the electrical signal has a difference of 0 to 2 times the optical loss. A difference of 20 dB occurs.

[0007] As described above, the output RF signal level transmitted from the antenna of the slave unit 4 may not be a problem even if the output level is slightly different in a system such as CATV in which a reproduced image is obtained by an image receiver directly connected to the antenna terminal. This does not occur, but in a mobile phone system that sends out radio waves with an antenna,
The range of radio waves differs and the size of the zone differs for each slave unit, which causes a problem. Therefore, the gain of the variable gain amplifier 46 is adjusted so that the difference in the loss of the optical cable when the slave unit is installed is corrected so that the transmission levels from the antennas are substantially equal so that the areas of the zones of the slave units are substantially equal. The installer is manually adjusting the installation. Therefore, there is a disadvantage that the installation work takes time.

Next, the RF due to the difference in the length of the optical cable 5
The difference between the transmission signal levels will be described. FIG. 4 shows an input RF when a light emitting diode is used as the E / O converter 32.
FIG. 4 is a diagram illustrating an example of a direct light intensity modulation characteristic showing a light modulation output with respect to a signal, and is a diagram illustrating a relationship between a current of a light emitting diode and a light output level. This indicates that when a high frequency signal (input RF signal) is superimposed on the bias current of the light emitting diode and driven, an analog intensity modulated optical output is obtained. When the modulation degree of the input RF signal is m, the optical output is A (1+
msin pt) cos ωt, and the converted dB when this output is demodulated is 2 × 10 log A + 20 logm [dB]. 10 log A [dB] of the first term of this equation is a light level.

FIG. 5 is a diagram for explaining the direct detection operation of the photodiode, and is a diagram for explaining the demodulation (detection) operation when a photodiode is used for the O / E converter 46 in FIG. When light having an optical input level A is input from the optical cable 5 to the photodiode, B flows as a current of the photodiode. Therefore, 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. That is, when the optical input is at the A level and the modulation degree of the RF signal a is m, the detected output RF current is b.

However, when the length of the optical cable 5 is long and the loss increases and the optical input level A is A ', the modulation m is constant and the current of the photodiode decreases to B', and the detected output RF The current becomes b 'and similarly decreases. The variable gain amplifier 46 needs to correct an amount by which the output RF signal b is reduced to b ′, that is, an increase in electric signal loss corresponding to twice the loss amount of the optical cable at which the optical input level A becomes A ′. In the above, the downlink from the parent device 3 to the child device 4 has been described, but the uplink has the same disadvantage.

As described above, the variable gain amplifier 46 must be manually adjusted when a new repeater device using conventional optical analog transmission is installed or the slave unit 4 is added. Measurement and adjustment, which requires labor and time.

It is an object of the present invention to provide a bidirectional communication system such as a portable telephone system in which the length of an optical cable due to the installation position when a plurality of slave units of the above-described conventional relay device using optical analog transmission are distributed is arranged. Uses an optical cable that automatically corrects for differences in received light levels due to differences, instead of manually adjusting it, significantly reducing the labor and time required for installation adjustments, and making the zones of each slave unit almost equal. It is an object of the present invention to provide a relay device that has been developed.

[0013]

A repeater according to a first embodiment of the present invention is directed to a first embodiment and converts a high-frequency electric signal of a downlink received from a radio base station into light. The light intensity modulation signal is distributed and output from a plurality of output terminals, and a plurality of uplink light intensity modulation signals input from a plurality of input terminals corresponding to the plurality of output terminals are respectively converted by a first optical / electrical converter. A base unit for detecting and converting to a high-frequency electric signal and then combining and transmitting a transmission wave to the wireless base station, a downlink optical cable connected to each of the plurality of output terminals and the plurality of input terminals; A plurality of pairs of optical cables, each of which is connected to an upstream optical cable, and a plurality of pairs of optical cables connected to each of the plurality of optical cables, A second optical-to-electrical converter detects a light intensity modulated signal received through the cable and converts it to a high-frequency electric signal, and sends out a transmission wave to the portable device, and transmits the high-frequency electric signal received from the portable device to the portable device. A plurality of slave units for outputting the light intensity modulated signal converted to light to the uplink optical cable, wherein the master unit is configured to receive the light intensity modulated signal from the plurality of slave units and to receive the light intensity modulated signal from the first unit. A plurality of first current detectors each detecting a DC current value of the optical / electrical converter as a detection value;
A plurality of variable gain amplifiers each amplifying the output signal of the electric converter, and respective detection values obtained from the plurality of first current detectors are compared with a preset reference value so that the difference becomes zero. A first control circuit for providing a control signal to the variable gain amplifier to perform a gain correction calibrated in advance to each of the plurality of slave units, wherein each of the plurality of slave units has the light intensity transmitted from the master unit to the slave unit. A second current detector for detecting a DC current value of the second optical / electrical converter to which a modulation signal is input as a detection value, and a variable current amplifier for amplifying an output signal of the second optical / electrical converter A gain amplifier;
A second control circuit for comparing the detected value obtained from the current detector with a preset reference value and providing a control signal to the variable gain amplifier for performing a gain correction that has been calibrated in advance so that the difference becomes zero. Wherein each level of the transmission wave transmitted from the plurality of slaves is substantially constant regardless of the length of a plurality of pairs of optical cables connected between the master and the plurality of slaves. It is characterized by being constituted so that it becomes. Further, the length of the plurality of pairs of optical cables is in a range of 1 m to 20 km.

[0014]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and the same parts as those in FIG. 2 are denoted by the same reference numerals. The difference from the conventional configuration is that the light receiving detection circuit portions of both the master unit 3 and the slave unit 4 have means for detecting the optical input level from the optical cable 5 and that the RF signal level detected by the detection level is substantially constant. That is, means for performing correction control is provided.

First, in the base unit 3, O / E converters 34-1 to 34-34 such as photodiodes for detecting upstream light transmitted from each of the slave units 4 via the optical cable 5 are provided.
current detector (I-DET) 35- for detecting the current value of n
O / E converters 34-1 to 34-n are provided.
And a variable gain amplifier 36-1 between the
To 36-n. The detection values detected by the current detectors 35-1 to 35-n are input to the control circuit 37. The control circuit 37 converts the detected current into a digital value by an A / D converter, estimates the loss of the optical cable from a DC current value of a reference value (a value when the length of the optical cable is 0 m), and adjusts the loss. A gain control signal is provided to the gain amplifiers 36-1 to 36-n so that the output level becomes a predetermined value to change the amplification degree. The DC current value and the gain correction value are calibrated in advance and stored in the memory of the control circuit 37.

Next, in the slave unit 4, the current value of the O / E converter 42, such as a photodiode, for detecting the downlink light transmitted from the master unit 3 via the optical cable 5 is detected by a current detector (I −DET) 44, and the control circuit 45
From the detected value, the loss of the optical cable is estimated from the DC current value when the length of the optical cable is 0 m, and the gain control is performed on the variable gain amplifier 46 similarly to the master station. The variable gain amplifiers 36-1 to 36-n and 46 may be variable attenuators, or may have a configuration in which an amplifier and a variable attenuator are combined.
When photodiodes are used as the O / E converters 34 and 42, as shown in FIG. 7, the current flowing through the photodiode changes linearly with the change in the optical input level.
That is, the O / O corresponding to the level of the input light received from the parent device 3 or the child device 4 of the relay device 2 via the optical cable 5
The DC current values of the E converters 42, 34 are detected by the current detectors 45, 3
5 to detect. The control circuits 37 and 45, for example, convert the detected current into a digital value using an A / D converter, estimate the loss of the optical cable from a DC current value of a reference value (for example, a value when the optical cable is 0 m), and adjust the loss. Gain amplifier 36, 4
The gain control signal is supplied to the variable gain amplifiers 36 and 46 so that the output RF signal voltage of No. 6 becomes a predetermined value to change the amplification degree. The DC current value versus the optical cable loss (actually, the gain of the variable gain amplifier) can be easily estimated because it is stored in advance in the memory of the control circuit.

[0017]

As described above in detail, by implementing the present invention, the output R output from the antennas of a plurality of slave units distributed over the optical cables 5 of different lengths is obtained.
The level of the F signal and the transmission level from the master unit to the base station can all be automatically made substantially equal. Therefore, it is necessary to set the variable gain range of the variable gain amplifier based on the distance from the installation point of the master unit to the installation point of the remote unit farthest from the size of the blind spot where the relay device is installed, the planar shape, and the like. Therefore, the labor and time required for installation adjustment for new installation or expansion can be greatly reduced, and the practical effect is extremely large.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a system configuration to which the present invention is applied.

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

FIG. 4 is a graph showing an example of electrical / optical conversion (direct modulation) characteristics.

FIG. 5 is a diagram illustrating an example of light / electric conversion (direct detection) characteristics and an operation of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 wireless base station 2 relay device 3 master unit 4 slave unit 5 optical cable 6 zone 31 radio unit 32 E / O converter 33 distributor 34 O / E converter 35 current detector 36 variable gain amplifier 37 control circuit 40 synthesizer 41 Radio unit 42 O / E converter 43 E / O converter 44 Current detector 45 Control circuit 46 Variable gain amplifier 48 Amplifier

 ──────────────────────────────────────────────────の Continued on the front page (72) Michio Norika, Inventor 3- 14-20 Higashinakano, Nakano-ku, Tokyo Inside Hitachi Kokusai Electric Co., Ltd. (72) Hiroshi Suzuki 3-14-20, Higashinakano, Nakano-ku, Tokyo Hitachi Kokusai Electric Co., Ltd. (72) Inventor Takashi Yokote 3-14-20 Higashinakano, Nakano-ku, Tokyo Stock Company Hitachi Kokusai Electric Co., Ltd. (72) Tadashi Akiyama 3-14-20, Higashinakano, Nakano-ku, Tokyo Stock Company Hitachi Kokusai Electric (72) Inventor Jun Suganuma 2-10-1, Toranomon, Minato-ku, Tokyo F-term in NTT DoCoMo, Inc. 5K067 AA21 BB02 BB21 BB43 DD42 DD43 DD44 EE02 EE06 EE10 EE37 GG08 GG09

Claims (2)

[Claims] An optical intensity modulation signal obtained by converting a downlink high-frequency electric signal received from a radio base station into light is output from a plurality of output terminals and output from a plurality of input terminals corresponding to the plurality of output terminals. A master unit for detecting a plurality of input optical intensity modulated signals of the uplink by a first optical / electrical converter, converting the detected signals into high-frequency electric signals, and combining and transmitting a transmission wave to the radio base station; A plurality of pairs of optical cables in which a downlink optical cable connected to each of the plurality of output terminals and an uplink optical cable connected to each of the plurality of input terminals are arranged in pairs; and A second optical / electrical converter detects a light intensity modulated signal which is connected to each of the optical cables and distributed and is received through the down-link optical cable. A plurality of slave units for transmitting a transmission wave converted into an electric signal to the portable device and outputting a light intensity modulation signal obtained by converting a high-frequency electric signal received from the portable device to light to the upstream optical cable. A plurality of first current detection units each detecting, as a detection value, a DC current value of the first optical / electrical converter to which the light intensity modulation signal is input from the plurality of slave units. , A plurality of variable gain amplifiers for respectively amplifying the output signal of the first optical / electrical converter, and a predetermined reference value for each detection value obtained from the plurality of first current detectors. A first control circuit that provides a control signal to the variable gain amplifier for performing a gain correction that is calibrated in advance so that the difference becomes 0, wherein each of the plurality of slave units is Transmitted to the handset A second current detector for detecting, as a detection value, a DC current value of the second optical / electrical converter to which the light intensity modulated signal is input, and an output signal of the second optical / electrical converter And a control signal for comparing the detection value obtained from the second current detector with a predetermined reference value and performing a gain correction calibrated in advance so that the difference becomes zero. A second control circuit to be provided to the variable gain amplifier, and transmitted from the plurality of slave units regardless of the length of a plurality of pairs of optical cables connected between the master unit and the plurality of slave units. A relay device using an optical cable, wherein each level of the transmission wave is configured to be substantially constant. 2. The length of the plurality of pairs of optical cables is 1 m or more.
2. The relay device according to claim 1, wherein the distance is within a range of 20 km.