This video shows the teardown of two Russian sensors. The first sensor is not a part of an Iskander missile but of a X101 missile.

00:00 Intro
00:25 Optical sensor from X101 missile
02:30 3axis Fiber Optic Gyroscope (probably from Tornado MLRS)

Links

A picture of the first sensor with the optics:
https://photo.unian.info/photo/117351...

Several viewers have found the technical documentation of the Fiber Optic Gyro:
http://www.optolink.ru/documents/trs...

Other information concerning the FOG:
https://en.defenceua.com/industries/...

Technical documentation in russian:
https://ela.kpi.ua/bitstream/12345678...