SNR improvement in a Raman based distributed temperature sensing system using a stimulated Raman scattering filter

In Raman-based distributed temperature sensing (DTS) systems, the signal to noise ratio (SNR) is often low due to weak backscattered Raman signals. This can limit both sensing distance and temperature resolution. Common methods of increasing the signal, versus noise floor, exist but most have significant limitations. For example, attempting to improve SNR by increasing the launching power is limited by the stimulated Raman scattering (SRS) threshold of the fiber. To overcome this power limitation, we propose a new SRS filtering method that allows more power to be launched into the fiber, beyond the SRS threshold, without causing additional temperature error. With this SRS filtering method we show that 3 dB more power may be launched into the fiber while improving the SNR of the received signals by 1.6 dB.