A novel loss-of-signal detector with programmable assert threshold for intelligent limiting amplifier

Abstract

This paper presents a novel programmable assert threshold loss-of-signal (LOS) detector with fixed optical hysteresis for intelligent limiting amplifier (LA) using 0.5-μm 2P2M CMOS technology. By adjusting the gain of the LA, a programmable threshold range of 2---20 mVpp is implemented. The proposed detector circuit obtains a signal strength indication voltage V SIG and a reference voltage V REF, both of which can be dependent each other. With other special circuit design techniques, the detector circuit achieves stable LOS range, LOS hysteresis and LOS precision, and all of them are completely independent on all process, voltage supply and temperature deviations. This LOS detector is integrated with a 155-Mbps LA operating at a compatible supply voltage of 3.3 and 5.0 V. The measurement results demonstrate that the LOS detector achieves a stable programmable assert threshold and a 2 dB fixed optical hysteresis for a 155 Mbps input pseudo random sequence.