Long coherence length interferometer

An interferometer has been developed which is capable of measuring the envelope of the coherence function of lasers whose mode lifetimes exceed 300 ns, corresponding to lengths over 100 m. The precision of this interferometer is determined to be 6.0%. The interferometer utilizes optical fibers for the purpose of optical delay. The minimum resolvable bandwidth of the interferometer is 64 kHz. This interferometer is capable of measuring not only the coherence function of a single laser, but also the mutual coherence function of coupled lasers. Its resolution is limited only by the total length of the interferometer and the losses in the optical fiber.