Optical branching equipment and optical network using the same

DETAILED DESCRIPTION It is therefore an object of the present invention to provide a low-cost optical branching equipment which permits switching of optical signal transmission lines without involving the conversion of an optical signal into an electrical signal, and hence is highly reliable and free from the necessity of maintenance for a long period of time.
Another object of the present invention is to provide an optical network which employs the above-mentioned optical branching equipment.
According to an aspect of the present invention, the optical branching equipment comprises: an optical divider means for branching an optical signal from a trunk line optical signal input terminal to a branching circuit and a short circuit; an optical coupler means for providing an optical signal from either the branching circuit or the short circuit to a trunk line optical signal output terminal; pump light supply means for supplying pump light of a predetermined wavelength; and an optical limiter amplifier means which is inserted in the short circuit and is held in an excited state by the incidence thereto of the pump light and which responds to the incidence of external control light to control the gain of amplification of an optical signal, thereby permitting or inhibiting the passage therethrough of the optical signal.
The optical network of the present invention, which employs the above-mentioned optical branching equipment, includes: a bus type trunk line including an optical fiber for transmitting an optical signal of a first wavelength; trunk line terminal equipment provided at one end of the trunk line, for transmission and reception of transmission information; the above-mentioned optical branching equipment inserted in the bus type trunk line; a branch line branched from the trunk line via the optical branching equipment and including an optical fiber for transmitting an optical signal; and branch line terminal equipment connected to the branch line, for adding and/or dropping transmission information, the branch line terminal equipment including a control light source for generating control light of a second wavelength and the branch line including means for supplying the control light to the optical branching equipment