| 摘要 |
PURPOSE:To estimate the degree of drift of a control voltage and to select an element which is kept free from a control failure by holding the elements at room temp. or a higher temp., continuously applying DC bias voltages of a prescribed value thereon, monitoring the phases of outputted light and selecting the element having a specific ratio of the drift quantity of the satd. voltage and the applied voltage. CONSTITUTION:The DC bias voltages of the arbitrarily specified value are continuously applied on the waveguide type electro-optic modulator element held in an environment at a specified temp. (preferably 30 to 100 deg.C) higher than room temp. and the element is operated in this state. The change of the operating point of the output light thereof with the lapse of time is monitored. The element which is at least smaller than 1 in the ratio A=VC/VB of the apparent satd. drift quantity VC determined with a voltage quantity as a unit from the change of the operating point of the output light with the lapse of time, i.e., DC drift, and the bias voltage VB applied thereon is selected. As a result, the easy sieving and sorting of the products are executed. The measurement time is shortened if the heating temp. is raised. The preferable measurement is executed at <=100 deg.C in order to suppress the thermal deterioration of adhesives. |
