Monitoring device and method for monitoring a fluid in subsea equipment, wherein the monitoring device includes a sensing element in contact with the fluid, at least one detector and a waveguide, where the sensing element is configured to implement an evanescent field absorption technique, the at least one detector is configured to detect an attenuated optical signal fed into the waveguide by at least one radiation source, and where the attenuation is caused by evanescent field absorption due to the fluid.
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