Optical transmission system for radio access and high frequency optical transmitter

• US 7,539,419 B2
• Filed: 01/30/2008
• Issued: 05/26/2009
• Est. Priority Date: 06/29/2000
• Status: Expired due to Fees

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Fuse, Masaru, Sasai, Hiroyuki
• Primary Examiner(s): CORS, NATHAN M
• Application Number:
  US12/010,866
• Publication Number:
  US 20080138076A1
• Time in Patent Office: 482 Days
• Field of Search: None
• US Class Current: 398/115
• CPC Class Codes: H04B 10/25753 Distribution optical network, e.g. between a base station and a plurality of remote units
• CPC Class Codes: H04B 10/25754 Star network topology

Abstract

Modulators respectively modulate baseband signals into IF signals having different frequencies. A multiplexer multiplexes the IF signals. An electrical-optical converter intensity modulates the multiplexed IF signals into optical signals. A local oscillation signal source outputs a predetermined local oscillation signal. An external modulator intensity-modulates the optical signal using the local oscillation signal. An optical branching portion branches the intensity-modulated optical signal and respectively outputs branched optical signals to radio base stations. An optical-electrical converter converts the optical signal into an electric signal, to obtain an RF signal by frequency-converting the IF signal. An antenna only transmits a component having a desired radio frequency extracted in a band filter from the RF signal to a subscriber terminal. Frequency conversion from the IF signal to the RF signal is thus optically performed, whereby the frequency or electrical-optical converter is shared among the radio base stations.

Claims

1. An optical transmission system comprising:

a center station; and

a plurality of radio base stations connected to the center station with a plurality of optical fibers, the plurality of radio base stations covering different service areas,

wherein said center station includes;

a light source for outputting predetermined light;

a local oscillation signal source for outputting a predetermined local oscillation signal;

an external modulation portion for intensity-modulating the light outputted from said light source using the local oscillation signal outputted from said local oscillation signal source;

an optical branching portion for branching an optical signal obtained by the intensity-modulating in said external modulation portion into a plurality of optical signals whose number corresponds to a number of said plurality of radio base stations; and

a plurality of IF modulation portions, which are provided so as to correspond to said plurality of radio base stations, each for intensity-modulating a respective one of the plurality of optical signals obtained, by the branching in said optical branching portion using an inputted electric signal, and outputting the intensity-modulated optical signal to a respective one of the plurality of optical fibers, and

wherein the electric signal inputted to each of the plurality of IF modulation portions is one or more IF signals in which one or more baseband signals are modulated by different predetermined intermediate frequencies respectively,

wherein each of said plurality of IF modulation portions intensity-modulates the respective optical signal such that a signal component, which includes an RF signal component used in a service area covered by a corresponding radio base station, is transmitted, and

wherein said plurality of radio base stations each, includes;

an antenna portion for transmitting and receiving radio signals to a subscriber terminal; and

at least an optical-electrical conversion portion for converting a corresponding one of the optical signals transmitted through the plurality of optical fibers into an electric signal in a radio frequency band, and feeding the converted electric signal to said antenna portion through a filter for extracting only the RF signal component.