In-chip temperature sensing and compensation for VCSEL driver ICs

Abstract

This thesis proposes a novel method of temperature compensation for VCSEL driver IC. The perfor-mance degradation due to temperature is one of the significant problems of optical transmitter in optical communication system. The output light power of the light source, especially VCSEL, decreases as tem-perature increases. In this method, temperature sensing (TS) circuit which can detect temperature as voltage level was used for compensating degradation of VCSEL driver IC. The additional current source which biased from TS circuit was located at drive stage of driver IC. The increase of current was obtained from the additional current source when temperature increases and it could sufficiently compensate temperature issue. This method does not need monitoring photodiode (M-PD), which could increase total chip area, while other method, automatic power control (APC), needs. Even though, the additional circuit, which is TS circuit, was used in proposed method, total area of TS circuit is only 104 ⅹ 78.8 um2. The proposed compensation method simulated with CMOS 0.13 um technology. This compensation method demonstrates 0.6 mA~16 mA of modulation current control, and it works up to 10 GHz with stable output performance until 95 ºC. The proposed compensation method with TS circuit demonstrates 98.725 % of output power compensation performance. The total current of compensated VCSEL driver IC which contains TS circuit is 24 mA, and the current consumption of only compensation module is 210.7 uA which is negligible. This method could modify like external component to control compensation sensitivity. Since TS circuit has quite small current consumption and chip area, it could be attached to anywhere. For example, it could be attached to each channel to detect each temperature in multi-channel system. And when Si VCSEL is developed, this TS chip could be applied within VCSEL. This in chip-integration with VCSEL would give stable and precise compensation performance. There...