Optical wavelength division multiplexed network system

An optical wavelength division multiplexed network system in which an optical fiber acting as a main trunk line interconnects a plurality of nodes in a ring form to permit communications between desired ones of said nodes, comprising:

• a multi-wavelength light source for multiplexing and transmitting a plurality of lights having different wavelengths;
• and
• optical splitting means for splitting and outputting lights transmitted from said multi-wavelength light source to both ends of said main trunk line for respective wavelengths;
• wherein each of said nodes includes an add-drop multiplexer for extracting light of a particular wavelength among the lights of a plurality of wavelengths transmitted via said main trunk line into the node and inserting the light of the preset wavelength from the node into the optical fiber acting as said main trunk line, at least one optical receiver for receiving part of the light extracted by said add-drop multiplexer, and a modulator for modulating the light extracted by said add-drop multiplexer with data to be transmitted and send the light back to said add-drop multiplexer, wherein first and second optical circulators connected to each other via a sub-trunk line are selectively connected between said main trunk line and input and output portions of each of said nodes by optical switches.

An optical wavelength division multiplexed network system based on an optical fiber ring system in which a cable of optical fiber is connected in a loop form to form a main trunk line between the light input and output terminals of a central node with a plurality of terminal nodes located in desired positions of said main trunk line to permit communications between desired ones of said terminal nodes via said central node, wherein said network system is a network in which different transmission wavelengths and reception wavelengths are assigned to said respective terminal nodes;

• said central node includes a multi-wavelength light source for generating lights of transmission wavelengths respectively assigned to said plurality of terminal nodes, optical wavelength division demultiplexer means for demultiplexing the optical signals from said main trunk line for respective wavelengths, opto-electronic converting means for receiving the optical signals of respective wavelengths demultiplexed by said optical wavelength division demultiplexer means, switching means for switching the electrical signals obtained in said opto-electronic converting means for respective destinations, electro-optic converting means for converting the electrical signals switched by said switching means into optical signals of wavelengths assigned to respective destination nodes, and optical wavelength division multiplexer means for multiplexing the optical signals transmitted by said electro-optic converting means and transmitting the multiplexed signal to said main trunk line;
• and each of said plurality of terminal nodes includes first optical wavelength division demultiplexer means for extracting optical signals of transmission wavelength and reception wavelength assigned to its own node from said main trunk line, second optical wavelength demultiplexer means for demultiplexing an optical signal of transmission wavelength and an optical signal of reception wavelength from the optical signal output of said first optical wavelength demultiplexer means, an optical receiver for receiving an optical signal of the reception wavelength demultiplexed by said second optical wavelength demultiplexer means, an optical modulator for modulating an optical signal of the transmission wavelength demultiplexed by said second optical wavelength demultiplexer means with data to be transmitted, and optical wavelength division multiplexer means for multiplexing the optical signal output from said optical modulator with optical signals which are not extracted by said first optical wavelength demultiplexer means and transmitting the multiplexed signal to said main trunk line.