Optical energy sensor and demodulation system - has etched single mode fibre stretched or compressed by signal energy to change optical path length

摘要

The signal energy to be sensed or detected is caused to stretch an etched single mode fibre. An etched single mode fibre is a single mode glass clad fibre whose cladding thickness has been reduced a specific amount so as to lower its strength. The invention provides that, when necessary to maintain the etched single mode fibre's light guiding properties, the portion of the glass clad which was removed is replaced with a plastic material whose optical index is lower than that of the single mode fibre's core material and whose elastic modulus is lower than that of the glass clad which it replaces. Such an etched single mode fibre is more sensitive to stretching or compression because it is weaker. For a given amount of signal energy, a single mode fibre will stretch a greater amount after it has been etched. The sensor is used in a hydrophone array.