Method and apparatus for duplex communication in hybrid fiber-radio systems

• US 20030231601A1
• Filed: 04/25/2003
• Published: 12/18/2003
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, A-jung
• Granted Patent: US 7,379,669 B2
• Time in Patent Office: Days
• US Class Current: 370/277
• CPC Class Codes: H04B 10/25752 Optical arrangements for wireless networks

Abstract

An apparatus and method for enabling cost-effective duplex communication by diplexing one of down stream signals for frequency up-conversion in a hybrid fiber-radio system includes diplexing an unmodulated mode signal among beating signals between a master laser and an injection-locked slave laser and using the diplexed signal for down-conversion in upstream transmission, thereby eliminating the need for expensive high-frequency local oscillators for frequency conversion. Higher radio frequency signals can be generated using beating between basic modes and satellite modes such as FWM conjugates of the master laser and slave laser. Cost-effective systems, stabilization of a light source and improved transmission performance may be achieved by using a diplexer instead of an expensive high-frequency local oscillator.

Claims

1. An apparatus for duplex communication in a hybrid fiber-radio system, the apparatus at a central office comprising:

an electrical signal source unit for generating RF signals;

a master laser driven by the electrical signals for generating optical signals;

a local oscillator for generating intermediate frequency signals;

a modulator for converting user source data into modulated signals;

a mixer for mixing the intermediate frequency signals from the local oscillator and the modulated signals from the modulator;

a slave laser for outputting an unmodulated optical signal at a lasing frequency and a modulated data signal at a down-converted frequency;

an optical routing device for feeding signals from the master laser to the slave laser and for launching signals from the slave laser over an optical transmission fiber;

a photodetector for receiving an optical signal from an upstream link.

2. An apparatus for duplex communication in a hybrid fiber-radio system, the apparatus at a remote station comprising:

an optical-to-electrical converter for converting received optical signals into electrical signals;

a diplexer for splitting data mode signals containing user source data and unmodulated mode signals;

a radio transmitter for converting the data mode signals into wireless radio signals and for transmitting the wireless radio signals wirelessly;

a radio receiver for converting received wireless radio signals into electrical signals;

a mixer for mixing diplexed signals and the electrical signals and outputting mixed electrical signals; and

a laser for converting the mixed electrical signals into optical signals.

3. A downlink transmission method in a method for duplex communication in a hybrid fiber-radio system comprising:

(a) generating an optical signal with a master laser driven by an RF source;

(b) generating an unmodulated optical beat signal with low phase noise by injecting the optical signal into a slave laser, and the optical signal locking the lasing mode of the slave laser;

(c) generating an intermediate frequency signal with a local oscillator;

(d) converting user source data into a modulated signal;

(e) mixing the intermediate frequency signal and the modulated signal to form a mixed signal;

(f) feeding the mixed signal to the slave laser, which outputs a data modulated beat signal at a lower side-band;

(g) transmitting an unmodulated mode signal and a data mode signal over an optical fiber with the routing operation of an optical routing device;

(h) converting a received optical signal into an electrical transmission signal;

(i) splitting with a diplexer the electrical transmission signal into a data mode signal containing user source data and the unmodulated mode signal;

(j) converting the data mode signal into a radio signal; and

(k) transmitting the radio signal wirelessly.

5. A computer-readable recording medium on which a program for executing the method claimed in claim 3 is recorded.

4. A method of uplink transmission in a method for duplex communication in a hybrid fiber-radio system comprising:

(a) converting signals wirelessly received by an antenna into electrical signals;

(b) mixing diplexed unmodulated mode signals with the electrical signals to form mixed electrical signals;

(c) down-converting a signal band of data;

(d) generating optical signals with a laser driven by the mixed electrical signals;

(e) transmitting the optical signals over an optical fiber; and

(f) receiving the optical signals with a photodetector at a central office.

6. A computer-readable recording medium on which a program for executing the method claimed in claim 4 is recorded.