| 摘要 |
PURPOSE:To simplify a circuit constitution and a scale by switching an optical output path in accordance with the input level of light through the use of the optical switching element of current control. CONSTITUTION:An optical fiber 1 is connected to the input-side of the optical switching element 2, and optical receivers 3 and 4, both of which have respectively different gains, are connected to the side of two outputs of the optical switching element 2. Input light is inputted to the optical switching element 2 through the optical fiber 1, and input light is segmented into the optical receivers 3 and 4 since the refractive index of the element 2 changes by a control current Icont. The segment operates to the optical receiver 3-side having the large gain when the optical level is small, and to the optical receiver 4-side having the small gain when the optical level is large. The control current uses that the optical current which occurs by the input optical level of a photodetector 5 flows into a resistance 6 and a resistance 7 and which generates a voltage. Thus, the dynamic ranges of respective receivers in sufficient with 1/2 of a whole system, and a control current circuit does not need a linear operation, whereby the circuit can be obtained by the simple constitution. |
