The optical transmission loss behavior was investigated for commercially available poly(methyl methacrylate) (PMMA) based polymer optical fibers (POFs). POFs were exposed to various climates of temperature and humidity. Optical transmission measurements using multiplexer (a prototype device) reveal that POFs exhibited an early drop-off followed by a slow decline of transmission at 1008C with low humidity and nearly 100% loss of transmission at the early stages of exposure at 928C with 95% relative humidity (RH) and at 1208C with low humidity. Fourier transform infrared (FTIR) and gel permeation chromatography (GPC) analysis data show no significant molecular changes in the PMMA core after climatic exposures. However, the attenuated total reflection (ATR)-FTIR data shows a few molecular changes in claddings due to degradation. Scanning electron microscopy (SEM) data illustrate the shrinkage and folding structure in claddings. The loss of the optical transmission at the early (initial) stages of exposure is attributed to the physical changes (like thermal expansion), and the same at the later stages mainly to chemical changes (e.g., oxidative degradation). The experiments conducted here show that the POFs optical transmission stability is strongly dependent on the chemical composition of claddings.

The optical transmission stability was investigated for commercially available polymer optical fibers (POFs) which were exposed to a climate of 928C and 95% relative humidity for about 3300 h. The optical transmission stability of POFs was correlated to their thermooxidative stability. POFs possessed identical core material, poly(methyl methacrylate), but they differed in the materials used for the claddings. The optical transmission was measured online using a prototype device called multiplexer. The chemiluminescence (CL) technique was applied to characterize the thermooxidative stability and degradation of POFs. CL analysis reveals the thermooxidative degradation of bare POFs (core and cladding), predominantly of the claddings, as a result of climatic exposure. Ultraviolet-visible transmittance measurements demonstrated more changes in the claddings as compared to the cores due to degradation. The CL and optical measurements data indicated that the optical transmission stability of POFs was dependent mainly on the thermooxidative stability of the claddings and their chemical compositions.

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