OPTICAL SIGNAL RECEIVER, OPTICAL SIGNAL ATTENUATION CONTROL METHOD AND OPTICAL SIGNAL ATTENUATION CONTROL CIRCUIT

PROBLEM TO BE SOLVED: To prevent damage to an optical module by making a VOA (Variable Optical Attenuator) normally function when the power of an optical interface device is turned on. SOLUTION: A VOA maximum attenuation control circuit 16 has a resistor 16d, a resistor 16f, a transistor 16e which is an emitter-follower type PNP transistor, and a capacitor 16g in addition to a conventional VOA maximum attenuation control circuit. At the moment at which the power of the optical interface device or an individual optical interface is shifted from an off-state to an on-state, since the charge of the capacitor 16g is 0 [V], a current I2 is supplied to the VOA 12 together with the shift to the on-state of the power by the transistor 16e. Thus, an attenuation amount of the VOA 12 becomes maximum. When the capacitor 16g is gradually charged, the base potential of the transistor 16e finally becomes +5 [V], and the current I2 becomes 0 [A]. Thereafter, an operation is shifted to the maximum attenuation control of the VOA 12 by an operational amplifier 16a. COPYRIGHT: (C)2010,JPO&INPIT