An optical simulator 10, shaped to be interchangeable with a complementary connector 7 that intermates with an optical connector 6 having an optical emitter 4 and an optical detector 5, comprises an alignment fixture 12 with connectors 21 and 22 for intermating with the optical emitter 4 and the optical detector 5, and an optical fiber 11 formed in a loop and installed within the alignment fixture 12 with a first end face 39 of the loop 11 aligned through a corresponding alignment fixture connector 24, with the emitter 4 and a second end face 37 of the loop 11 aligned through a corresponding alignment fixture 25, with the detector 5 of the optical connector 6. The optical fiber 11 is formed in a loop further with a film forming a thin membraceous skin on an end of the optical fiber to provide controlled attenuation of optical power to the detector 5.