Method for gain control of fiberoptic repeating system

• US 6,980,739 B1
• Filed: 12/22/1999
• Issued: 12/27/2005
• Est. Priority Date: 12/26/1998
• Status: Expired due to Fees

• Current Assignee: LG-Ericsson Company Limited (Telefonaktiebolaget LM Ericsson)
• Original Assignee: LG Information & Communications Ltd. (LG Corporation)
• Inventors: Hong, Ik Pyo
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Li, Shi K.
• Application Number:
  US09/469,308
• Time in Patent Office: 2,197 Days
• Field of Search: 359174-179, 379/56.1, 379/56.2, 370/247, 370/310.1, 370/310.2, 398/173, 398/115, 398/28, 398/32, 398/33, 398/158
• US Class Current: 398/32
• CPC Class Codes: H04B 10/25759 Details of the reception of RF signal or the optical conversion before the optical fibre
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A method of gain control in a fiberoptic repeating system is disclosed. By the present invention, the signal levels of an optical cable can be frequently monitored without affecting the control operations of the base station. Thus, damped signal levels can effectively be compensated.

Claims

1. A method for a gain control of a fiberoptic repeating system comprising:

determining whether a control signal of a base station has been received;

outputting a locally generated modulated MODEM signal at a predetermined level based on whether the control signal of the base station has been received, and if the control signal has been received outputting the MODEM signal at a level different from said predetermined level;

if the control signal has not been received, mixing from a master repeater the locally generated modulated MODEM signal of said predetermined level with a RF signal and transmitting the mixed signal through an optical cable;

detecting at a slave repeater a modulated MODEM signal level from the mixed signal transmitted by the master repeater;

comparing, at the slave repeater, the detected modulated MODEM signal level with a reference level and obtaining a difference between the levels, wherein the reference level corresponds to said predetermined level unless the master repeater transmits the control signal of the base station; and

adjusting a gain of an amplifier for the RF signal in the slave repeater by using the obtained difference to calculate the gain adjustment, wherein the modulated MODEM signal is generated independently from the RF signal.

2. A method of claim 1, wherein the modulated MODEM signal is detected by a controller of a slave repeater.

3. A method of claim 1, wherein controlling the gain of the amplifier comprises increasing a level of the RF signal by the obtained difference.

4. A method for a fiberoptic repeating system comprising:

receiving from a base station a first RF signal;

amplifying the first RF signal by a constant level through an amplifier of a master repeater;

determining whether a control signal of the base station has been received;

outputting a locally generated first modulated MODEM signal at a predetermined level based on whether the control signal of the base station has been received, and if the control signal has been received outputting the first MODEM signal at a level different from said predetermined level;

if the control signal has not been received, mixing the locally generated first modulated MODEM signal of said predetermined level with the first amplified RF signal and transmitting the mixed signal through an optical cable to a slave repeater;

receiving and separating the mixed signal into a second modulated MODEM signal and a second RF signal, and detecting a modulated MODEM signal level from the second modulated MODEM signal;

comparing, at the slave repeater, the modulated MODEM signal level with a reference level and obtaining a difference between the levels, wherein the reference level corresponds to said predetermined level unless the master repeater transmits a control signal of the base station;

controlling a gain of an amplifier for the RF signal in the slave repeater based upon said obtained difference; and

amplifying the second RF signal according to the controlled gain and transmitting the second amplified RF signal to terminal, wherein the first modulated MODEM signal is generate independently from the RF signal.

5. A method of claim 4, wherein the modulated MODEM signal level is detected by a controller of the slave repeater.

6. A method of claim 4, wherein controlling the gain of the amplifier for the RF signal in the slave repeater comprises increasing a level of the second RF signal by the obtained difference.

7. A method of controlling gain in a fiberoptic communication system, comprising:

determining whether a control signal of a base station has been received;

outputting a locally generated monitoring signal of a predetermined level based on whether the control signal of the base station has been received, and if the control signal has been received outputting the monitoring signal at a level different from said predetermined level;

if the control signal has not been received, combining the locally generated monitoring signal of said predetermined level with an RF signal, wherein the monitoring signal comprises a modulated gain control signal;

transmitting the combined monitoring and RF signals to a slave repeater;

receiving and separating the transmitted monitoring signal from the transmitted RF signal at the slave repeater;

comparing, at the slave repeater, a level of the received monitoring signal with said predetermined level; and

adjusting a gain applied to the received RF signal by using a result of the comparison to calculate the gain adjustment, wherein the monitoring signal is generated independently from the RF signal.

8. The method claim 7, wherein the transmitting step comprises:

converting the combined monitoring and RF signals into an optical signal; and

transmitting the optical signal to the slave repeater via an optical fiber.

9. An optical repeater system, comprising:

a master repeater configured to receive an RF signal and generate a modulated reference signal having a level determined based whether a control signal of a base station is received, wherein the reference signal has a predetermined level if the control signal is not received and has a level different from said predetermined level if the control signal is received, said master repeater further combining the RF signal with the modulated reference signal, and converting the mixed signal to an optical signal for transmission over an optical cable; and

a slave repeater, configured to receive the optical signal from the optical cable, convert the optical signal to a received mixed signal, split the received mixed signal into a received RF signal and a received modulated signal, compare the received modulated signal to a reference value corresponding to said predetermined level unless the master repeater received the control signal of the base station, and amplify the received RF signal according to a result of the comparison, wherein the modulated reference signal is generated independently from the RF signal.

10. The optical repeater system of claim 9, wherein the master repeater comprises a modem to generate the modulated signal, and wherein the slave repeater comprises a modem to demodulate the received modulated signal.