Optical micro cell transmission system

• US 5,615,034 A
• Filed: 11/27/1995
• Issued: 03/25/1997
• Est. Priority Date: 11/25/1994
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hori, Tsuguo
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/563,203
• Time in Patent Office: 484 Days
• Field of Search: 359/110, 359/143, 359/145, 359/146, 359/153, 359/161, 379/59
• US Class Current: 398/158
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems

Abstract

An optical micro cell transmission system comprising a radio base station, at least one optical interface section connected to the radio base station, and an optical forward base station connected to the optical interface section via optical fibers for transmitting and receiving signals through an antenna, and being flexible for the variation of an amplifier due to a change in temperature or a change in the length of an optical segment, and also being available for detecting faults in the optical forward base station is provided. Pilot signal generators 30, 51 are provided for generating pilot signals. For a transmitted signal 11, a coupler 21 in the optical interface section convolutes a pilot signal P_D, and a demodulator 48 in an optical forward base station detects the level of the pilot signal P_D and controls a downward signal amplifier 42 according to the result of detection. For a received signal received by an antenna 6, a coupler 45 in the optical forward base station convolutes a pilot signal P_U, a demodulator 27 in the optical interface section detects the level of the pilot signal P_U and controls an upward signal amplifier 25 according to the result of detection. Furthermore, control signals and fault information signals are transmitted in a modulated signal for the pilot signals P_D, P_U.

Claims

1. An optical micro cell transmission system comprising:

a radio base station;

at least one optical interface section connected to said radio base station;

an optical forward base station connected to said optical interface section via an optical fiber and connected to an antenna;

a first pilot signal mixing means in said optical interface section for mixing a downward transmitted signal from said radio base station with a first pilot signal generated in said optical interface section, thereby producing a first mixed signal, and transmitting said first mixed signal to said optical forward base station;

a first signal adjusting means in said optical forward base station for receiving and amplifying said first mixed signal from said optical interface section, and for separating said first pilot signal from said downward transmitted signal to be transmitted through said antenna from said first mixed signal;

a first control means in said optical forward base station for measuring a level of said separated first pilot signal, and for controlling said first signal adjusting means to adjust amplification of said first mixed signal with reference to the measured level of said first pilot signal;

a second pilot signal mixing means in said optical forward base station for mixing an upward transmitted signal received from said antenna with a second pilot signal generated in said optical forward base station, thereby producing a second mixed signal, and transmitting said second mixed signal to said optical interface section;

a second signal adjusting means in said optical interface section for receiving and amplifying said second mixed signal from said optical forward base station, and for separating said second pilot signal from said upward transmitted signal to be transmitted to said radio base station from said second mixed signal; and

a second control means in said optical interface section for measuring a level of said separated second pilot signal, and for controlling said second signal adjusting means to adjust amplification of said second mixed signal with reference to the measured level of said second pilot signal.

2. An optical micro cell transmission system including a radio base station, at least one optical interface section connected to said radio base station, and optical forward base station connected to said optical interface section via an optical fiber and to which an antenna is connected, said optical micro cell transmission system comprising:

a first pilot signal convolution means installed in said optical interface section for convoluting a downward transmitted signal from said radio base station with a first pilot signal, comprising;

a first pilot signal generator for generating said first pilot signal; and

a first coupler for coupling said first pilot signal to said downward transmitted signal from said radio base station;

a first control means installed in said optical forward base station for detecting the variation of the level of said first pilot signal to control a signal level of the transmitted signal to be output from said optical forward base station, comprising;

a first variable amplifier the amplification degree for which is controlled by a first amplification degree control signal for amplifying signals from said optical interface section;

a first branching device installed at the output of said first variable amplifier for obtaining said first pilot signal;

a first detection means for detecting the level of said first pilot signal obtained from said first branching device; and

a first controller for comparing the level of said detected first pilot signal to a first predetermined value to output said first amplification degree control signal;

a second pilot signal convolution means installed in said optical forward base station for convoluting a received signal received by said antenna with a second pilot signal, comprising;

a second pilot signal generator for generating second pilot signal; and

a second coupler for coupling said second pilot signal to said received signal from said antenna; and

a second control means installed in said optical interface section for detecting the variation of the level of said second pilot signal to control a signal level of the upward received signal to be output to said radio base station, comprising;

a second variable amplifier the amplification degree for which is controlled by a second amplification degree control signal for amplifying signals from said optical forward base station;

a second branching device installed at the output of said second variable amplifier for obtaining said second pilot signal;

a second detection means for detecting the level of said second pilot signal obtained from said second branching device; and

a second controller for comparing the level of said detected second pilot signal to a second predetermined value to output said second amplification degree control signal.

3. An optical micro cell transmission system according to claim 2 wherein,

said first pilot signal convolution means further comprising:

a first modulator connected to said first pilot signal generator for modulating control signals to be transmitted to said optical forward base station from said second controller with said first pilot signal; and

said first detection means further comprising;

a first demodulator for demodulating said first pilot signal, detecting signal level of said first pilot signal and extracting control signals for controlling said optical forward base station by said first controller.

4. An optical micro cell transmission system according to claim 2 wherein,

said second pilot signal convolution means further comprising:

a second modulator connected to said second pilot signal generator for modulating fault signals to be transmitted to said optical interface section from said first controller with said second pilot signal; and

said second detection means further comprising;

a second demodulator for demodulating said second pilot signal, detecting signal level of said second pilot signal and extracting fault signals of said optical forward base station for informing a fault state by said second controller.

5. An optical micro cell transmission system including a radio base station, at least one optical interface section connected to said radio base station, and optical forward base station connected to said optical interface section via an optical fiber and to which an antenna is connected, said optical micro cell transmission system comprising:

a first pilot signal convolution means installed in said optical interface section comprising;

a first pilot signal generator for generating a first pilot signal;

a first coupler for coupling said first pilot signal to a downward transmitted signal from said radio base station; and

a first modulator connected to said first pilot signal generator for modulating control signals to be transmitted to said optical forward base station from a second controller with said first pilot signal;

a first control means installed in said optical forward base station comprising;

a first variable amplifier the amplification degree for which is controlled by a first amplification degree control signal for amplifying signals from said optical interface section;

a first branching device installed at the output of said first variable amplifier for distributing input signals to said first pilot signal and transmitted signals to be output through said antenna;

a first demodulator for demodulating said first pilot signal obtained from said first branching device, detecting signal level of said first pilot signal and extracting control signals; and

a first controller for comparing the level of said detected first pilot signal to a first predetermined value to output said first amplification degree control signal, and controlling said optical forward base station by said extracted control signals;

a second pilot signal convolution means installed in said optical forward base station comprising;

a second pilot signal generator for generating a second pilot signal;

a second coupler for coupling said second pilot signal to a received signal from said antenna; and

a second modulator connected to said second pilot signal generator for modulating fault signals to be transmitted to said optical interface section from said first controller with said second pilot signal; and

a second control means installed in said optical interface section comprising;

a second variable amplifier the amplification degree for which is controlled by a second amplification degree control signal for amplifying signals from said optical forward base station to said radio base station;

a second branching device installed at the output of said second variable amplifier for distributing input signals to said second pilot signal and said received signal to be output to said radio base station;

a second demodulator for demodulating said second pilot signal, detecting signal level of said second pilot signal obtained from said second branching device and extracting fault signals of said optical forward base stations; and

a second controller for comparing the level of said detected second pilot signal to a second predetermined value to output said second amplification degree control signal, and informing a fault state of said optical forward base station to said radio base station in accordance with said extracted fault signals.

6. An optical micro cell transmission system comprising:

a radio base station;

at least one optical interface section connected to said radio base station;

an optical forward base station connected to said optical interface section via an optical fiber and connected to an antenna;

a first pilot signal mixing means in said optical interface section for mixing a downward transmitted signal from said radio base station with a first pilot signal;

a first control means in said optical forward base station for detecting a variation of a level of said first pilot signal to control a signal level of the transmitted signal to be output from said optical forward base station;

said first control means including;

a first variable amplifier, an amplification degree for which controlled by a first amplification degree control signal for amplifying signals from said optical interface section;

a first branching device at the output of said first variable amplifier for obtaining said first pilot signal;

a first detection means for detecting the level of said first pilot signal obtained from said first branching device; and

a first controller for comparing the level of said detected first pilot signal to a first predetermined value to output said first amplification degree control signal;

a second pilot signal mixing means in said optical forward base station for mixing a received signal received by said antenna with a second pilot signal; and

a second control means in said optical interface section for detecting a variation of a level of said second pilot signal to control a signal level of the upward received signal to be output to said radio base station, said second control means including;

a second variable amplifier, an amplification degree for which controlled by a second amplification degree control signal for amplifying signals from said optical forward base station;

a second branching device at the output of said second variable amplifier for obtaining said second pilot signal;

a second detection means for detecting the level of said second pilot signal obtained from said second branching device; and

a second controller for comparing the level of said detected second pilot signal to a second predetermined value to output said second amplification degree control signal.

7. An optical micro cell transmission system comprising:

a radio base station;

at least one optical interface section connected to said radio base station;

an optical forward base station connected to said optical interface section via an optical fiber and connected to an antenna;

a first pilot signal mixing means in said optical interface section for mixing a downward transmitted signal from said radio base station with a first pilot signal, said first pilot signal mixing means including;

a first pilot signal generator for generating first pilot signal;

a first coupler for coupling said first pilot signal to said downward transmitted signal from said radio base station;

a first control means in said optical forward base station for detecting a variation of a level of said first pilot signal to control a signal level of the transmitted signal to be output from said optical forward base station;

a second pilot signal mixing means in said optical forward base station for mixing a received signal received by said antenna with a second pilot signal, and said second pilot signal mixing means including;

a second pilot signal generator for generating second pilot signal; and

a second coupler for coupling said second pilot signal to said received signal from said antenna;

a second control means in said optical interface section for detecting a variation of a level of said second pilot signal to control a signal level of the upward received signal to be output to said radio base station.