The loss of stability of frequency remote transmission problems caused by fiber channel characteristics is studied. The unstability is introduced by integrated fiber thermal expansion, refractive instability distribution and dispersion effects characteristic changing with temperature. A link delay model is established. 1550 nm signal transmission experiment through the 25 km single mode fiber model is validated. Experimental results show that the theoretical calculated delay variation and experimental results of the model stay consistent, when the optical fiber temperature and environmental temperature change synchronized and other environmental factors have little effect on the stability of the transmission. The model is discussed and the changes of model parameters caused by temperature and wave length are determined, and the order of magnitudes of various features introduced to delay is obtained. When the relative delay caused by changes of refractive index change turns to 10.22 ns, the fiber thermal expansion and dispersion effects caused delays are 0.7741 ns and -0.5983 ps respectively.