Optical local area network system and node apparatus used in the same

An optical LAN system, comprising:

• a plurality of node apparatus each being assigned with an address wavelength which is different from wavelengths assigned to other node apparatus;
• and
• an optical fiber transmission line for connecting said plurality of node apparatus;
• wherein each of said plurality of node apparatus in receiving mode supplies a light of said address wavelength on said optical fiber transmission line, and where a first node apparatus selected from said plurality of node apparatus has no data transmission request, lights supplied from said plurality of node apparatus excluding said first node apparatus are passed through said first node apparatus, and only that light supplied from said first node apparatus and propagated through said optical fiber transmission line is pulled in said first node apparatus, and where said first node apparatus has a data transmission request to a second node apparatus selected from said plurality of node apparatus, a light supplied from said second node apparatus is modulated by data in said first node apparatus to be supplied on said optical fiber transmission line.

A node apparatus used in an optical LAN system, comprising:

• a fixed wavelength optical filter having first and second input terminals and first and second output terminals, said fixed wavelength optical filter being supplied at said first input terminal with wavelength division multiplexed light including an address wavelength inherently assigned to said node apparatus to output a light of said address wavelength at said second output terminal and said wavelength division multiplexed light excluding said address wavelength at said first output terminal, and at said second input terminal with a light of said address wavelength to output said light of said address wavelength at said first output terminal;
• a first optical to electric converter for converting said light of said address wavelength supplied from said second output terminal of said optical fixed wavelength filter to a first electric signal;
• a light emitting device for providing said second input terminal of said optical fixed wavelength filter with a light of said address wavelength;
• a tunable wavelength optical filter having first and second input terminals and first and second output terminals, said tunable wavelength optical filter being supplied with said lights of said multiplexed wavelengths at said first input terminal to output a light of a destination address wavelength selected from said multiplexed wavelengths at said second output terminal and lights of said multiplexed wavelengths excluding said destination address wavelength and said light of said destination address wavelength modulated by a transmitting data supplied to said second input terminal thereof at said first output terminal;
• an optical modulator for providing said first input terminal of said optical variable wavelength filter with said light of said destination address wavelength modulated by said transmitting data;
• and
• an access processing circuit for receiving said first electric signal to generate a data transmitted to said node apparatus and driving said modulator by said transmitting data.

A node apparatus used in an optical LAN system, comprising:

• an optical wavelength demultiplexer for demultiplexing multiplexed wavelengths supplied from an optical transmission line to a plurality of lights having a wavelength different from each other;
• an optical to electric converter for converting one of said lights having an address wavelength inherently assigned to said node apparatus to an electric signal;
• means for determining a modulating signal by which said electric signal has been modulated;
• an access processing circuit for demodulating said electric signal to generate a transmitted data and determining a node apparatus from which said transmitted data is received in accordance with said modulating signal;
• means for modulating one selected from said plurality of said lights excluding said light of said address wavelength by a transmitting data;
• a light emitting device for emitting a light of said address wavelength;
• and
• an optical wavelength multiplexer for said plurality of lights supplied from said optical wavelength demultiplexer excluding said light supplied to said optical to electric converter, one of which is modulated by said means for modulating, and said light supplied from said light emitting device to provide an optical fiber transmission line with lights of said multiplexed wavelengths to be propagated therethrough.