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We present two configurations of an amplified fiber-optic-based corrosion sensor using the optical time domain reflectometry (OTDR) technique as the interrogation method. The sensor system is multipoint, self-referenced, has no moving parts and can measure the corrosion rate several kilometers away from the OTDR equipment. The first OTDR monitoring system employs a remotely pumped in-line EDFA and it is used to evaluate the increase in system reach compared to a non-amplified configuration. The other amplified monitoring system uses an EDFA in booster configuration and we perform corrosion measurements and evaluations of system sensitivity to amplifier gain variations. Our experimental results obtained under controlled laboratory conditions show the advantages of the amplified system in terms of longer system reach with better spatial resolution, and also that the corrosion measurements obtained from our system are not sensitive to 3 dB gain variations.

For the development of optical sensors, we investigate the advantages of employing an erbium doped fiber amplifier (EDFA) in a sensor system based on optical time domain reflectometry (OTDR). We first characterize the EDFA using the OTDR in terms of gain, insertion loss and pumping configurations. Then we compare the system performance with and without amplification. Our experimental results indicate that the use of the amplified OTDR system can increase the total reach of the sensor system.

Several approaches have been proposed in order to solve the adaptive control of optical amplifier operating point problem (ACOP). These approaches aim to adjust the gain of each amplifier in a cascade of amplifiers. Some previous resultsshow that it is possible to decrease the noise added by the amplifiers by using these strategies. However, the configurations found by these approaches may degrade the quality of the transmission due to nonlinear effect, because the amplifiers may operate with a high output power. Therefore, the goal of this work is to analyze the impact of the nonlinear effects in the solutions found by these approaches by evaluating the BER of a system that uses a very sensitive modulation in terms of OSNR (64QAM). We tested LossComp, WAdGC and AsHB approaches in a system with 40 channels, using SOGHz fixed grid and considering high and low system input powers. The results showed that for all analyzed approaches the system quality of transmission is affected by the nonlinear effects, and the effect is worse in those with higher amplifier output powers.

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