Abstract: A wavelength dispersion compensation apparatus is provided which requires only a small number of dispersion compensation fibers for compensating for the wavelength dispersion of a wavelength multiplex signal caused in the transmission optical fibers. The dispersion compensation fibers are used for transmitting individual light signals which composes a wavelength multiplex signal, in order to give a wavelength dispersion in the opposite direction, the absolute value of which is the same as the dispersion which will be caused in the light signals during transmitting in the transmission optical fibers. At the output ends of the dispersion compensation fibers, a pair of two light signals with specific wavelengths is extracted by the light branching means composed of fiber gratings FG11 and FG12 and so on. The light signals extracted by the light branching means are multiplexed by the arrayed waveguide AWG2 and supplied to the transmission optical fibers after amplified by the light amplifiers AMP1 to AMP8.

Abstract: An automatic optical output level adjuster has a plurality of couplers for branching an optical signal, an optical switch for switching optical signal paths, a variable attenuator for attenuating the optical signal, a variable optical amplifier for amplifying the optical signal, photodetectors, and a CPU for control. The photodetectors detect the level of an optical input to the automatic optical output level adjuster and the level of an optical output from the adjuster. The CPU controls the optical switch on the basis of the detected optical input level and controls the amount of attenuation by the variable attenuator or the optical output from the variable amplifier on the basis of the detected optical output level.

Abstract: Disclosed is an optical divider with three input ports and three output ports for dividing an optical signal, which has: three base circuits, each of which having a first optical coupler which is connected to a predetermined input port of the three input ports and outputs a first optical signal and a second optical signal by dividing an optical signal to be input to the predetermined input port in two directions, an optical switch which has two optical signal inputs and one optical signal output which is connected to an output port of the three output ports which is paired with the predetermined input port and selects either of two optical signal to be input to the two optical signal inputs by using the first optical signal as a selection signal to output it from the optical signal output, and a second optical coupler where the second optical signal is input and then is further divided into a third optical signal and a fourth optical signal in two directions; wherein the third and fourth optical signals of on