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

• US 7,379,669 B2
• Filed: 04/25/2003
• Issued: 05/27/2008
• Est. Priority Date: 04/25/2002
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, A-jung
• Primary Examiner(s): TRAN, DZUNG D
• Application Number:
  US10/423,760
• Publication Number:
  US 20030231601A1
• Time in Patent Office: 1,859 Days
• Field of Search: 398 66- 68, 398 72- 76, 398/115, 398/121
• US Class Current: 398/74
• 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 RF signals from the source unit 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 to generate a mixed signal;

a slave laser for outputting an unmodulated non-data optical signal at a lasing frequency and for generating a modulated data signal from the mixed signal at a down-converted frequency;

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

a photodetector for receiving an optical signal from the optical transmission fiber.

2. 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 non-data mode signal with low phase noise by injecting the optical signal into a slave laser, and using the optical signal to lock 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 mode signal at a lower side-band;

(g) transmitting an unmodulated non-data 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 from the optical fiber 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 non-data mode signal;

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

(k) transmitting the radio signal wirelessly.

3. An article of manufacture having a machine-accessible medium including data that, when accessed by a machine, cause the machine to perform the method claimed in claim 2.

4. A communication system, comprising:

a central station and remote stations, wherein the central station includes;

a radio signal generator;

a master laser driven by the radio signal generator to produce optical signals;

an oscillator for generating intermediate frequency signals;

a modulator for converting user data into modulated signals;

a mixer for combining the intermediate frequency signals and the modulated signals to form a mixed signal;

a slave laser for outputting an unmodulated non-data optical signal at a lasing frequency and for generating a modulated data signal from the mixed signal at a down-converted frequency;

an optical routing device; and

a photodetector.

5. The communication system as claimed in claim 4, wherein the radio signal generator drives the master laser using a direct modulation method.

6. The communication system as claimed in claim 4, wherein the optical routing device routes signals from the master laser to the slave laser and launches signals from the slave laser over an optical transmission fiber.

7. The communication system as claimed in claim 4, wherein the optical routing device injects the optical signals of the master laser into the slave laser to lock a lasing mode of the slave laser and generate an unmodulated optical beat signal.