OPTICAL DETECTION DEVICE

PROBLEM TO BE SOLVED: To provide an optical detection device capable of accurately deciding the live-line state of an optical fiber, etc., and preventing erroneous decision. SOLUTION: This optical detection device is provided with a photodiode (PD) 101 for receiving light from the optical fiber and generating the photovoltaic force of a voltage level that corresponds to the light receiving quantity, a terminal connecting and switching device 103 having a terminal T0 connected to terminals T1, T2 and T3 in fixed intervals, an operational amplifier 105 being an inverted amplifier, a current limiter resistor Rs for making current supplied to the amplifier 105 from a power supply voltage Vcc a minimum input current that can be amplified by the amplifier 105, a preamplifier part 107 for further amplifying an output voltage amplified by the amplifier 105, a light emitting diode (LED) 109 for an indicator for emitting light in accordance with the output voltage from the preamplifier 107 and variable resistor VR1 to VR3, and decides the live-line state of the optical fiber on the basis of a light emitting display pattern displayed by the LED 109.