| 摘要 |
PURPOSE:To easily and exactly detect whether an optical signal is received or not regardless an error rate, by deciding directly the reception level of the optical signal. CONSTITUTION:A reception signal AS is obtained at an arbitrary time slot, and when it is decided that the level of a bipolar reception signal BS is lower than a threshold value Vth generated from a threshold value voltage generation circuit 20 by a comparator 21, a pulse signal FS outputted from a one-shot multivibrator 23 goes to an 'H' level continuously, As a result, an alarm signal IS of the.,H,. level which represents the reception of an optical burst signal is generated from a D flip-flop 24. Meanwhile, since no comparison output('M' level) CS is outputted from a comparator 21 when no reception signal of a constant level or more arrives, the alarm signal IS of an '' level which represents that no optical burst signal arrives from the D flip-flop 24, is generated. In this way, by setting the threshold value Vth corresponding to the identifying processing capability of a reception data, it is possible to surely detect the presence/absence of the reception signal with simplified constitution. |
