Patent ID: 6304351
Filing Date: 2001-10-16
Classification: G02B,H04J,H04Q

Abstract:
A system using a single fiber pair for carrying branch traffic from a plurality of branching units attached to a plurality of trunk fibers, comprising:a plurality of optical fiber trunks for carrying trunk traffic;a plurality of branching units, each attached to one said fiber trunks, and each having an add and drop port;a first reflective filter in each of said branching units for passing said branch traffic from said add port to said drop port of each of said branching units; anda single fiber pair connecting said branching units for carrying branch traffic between said branching units, wherein at least one of said branching units includes:first and second cross bar switches each having at least a first, second and third ports such that in a first state said first cross bar directs an optical signal appearing on the first port to the second output port and in a second state said first cross bar directs the optical signal from the first port to the third port;a reflective filter coupling said third port of the first switch to said third port of the second switch, said reflective filter being configured to reflect a prescribed wavelength and to transmit therethrough all remaining wavelengths forming the WDM signal;an optical fiber coupling the second port of the first switch to the second port of the second switch;first and second circulators each having an input, output and intermediate ports, said intermediate port of said first and second circulators being coupled to said first port of said first and second switches, respectively;wherein said input port of said first circulator is adapted to receive the WDM signal from the transmitting terminal and said output port of said first circulator is adapted to receive said prescribed wavelength and transmit said prescribed wavelength to a branching terminal, and further wherein said input port of said second circulator is adapted to receive the prescribed wavelength from a branching terminal and said output port of said second circulator is adapted to receive the WDM signal and transmit the WDM signal to a receiving terminal.