We successfully fabricated plastic ferrules and split alignment sleeves for single-mode fiber-optic connectors by the injection molding process. Liquid crystalline polymer (LCP) was used as the molding material for the ferrule. We introduced an eccentricity control mechanism into the ferrule mold and realized an eccentricity of less than 1 µm. As the molding material for the sleeve, thermosetting epoxy resin was used. Suitable mechanical properties were realized by employing appropriate dimensional design and the molding process. The optical characteristics of a system combining these plastic components are compatible with single-mode SC-type connectors and are also stable under hot and humid conditions.

We successfully fabricated split alignment sleeves for single-mode operation with the injection-molding technique using both thermosetting epoxy resin and thermoplastic polyetherimide (PEI) resin. The relationship between the surface smoothness and the connection-loss characteristics of these injection-molded plastic sleeves was investigated. We made two-dimensional contour maps of the outer and inner surfaces of the plastic sleeves using the measured surface roughness. There were many contour lines on both the outer and inner surfaces of the PEI sleeve. In contrast, the epoxy sleeves had very smooth surface profiles. An offset Δr was estimated by using the inner-surface roughness data of the sleeve-ferrule contact regions. The connection loss of the sleeve increased as the Δr value increased. The measured losses agree fairly well with the theoretical losses estimated by using the Δr values. The PEI sleeves exhibited large Δr values, and one-third of them had large connection losses of > 0.5 dB. In contrast, the epoxy sleeves had very small Δr values of < 0.6 µm, and exhibited an average loss of < 0.1 dB.

We examined the creep properties and hazard rates of plastic ferrules to ensure the long-term reliablity of optical fiber connections. The endface deformation ΔL had to be smaller than 3 µm to keep the insertion-loss and return-loss fluctuation to acceptable levels in the worst case of random concatenation of similarly deformed plastic ferrules. From the fluctuation data, we estimated the time-to-failure tf at which the ΔL value became 3 µm. We estimated the acceleration parameters, median lifetimes ξ, and hazard rates λ by using tf values based on Weibull statistics. The ξ values decreased rapidly with increasing temperature and relative humidity. We found we could expect small λ values of < 0.1 FIT (FIT=10-9/hour) and of 1 FIT for 20 years in a normal atmosphere (25C/50%RH) and in a more severe case of 25C/90%RH, respectively.

We examined the creep properties and hazard rates of plastic split alignment sleeves to ensure the long-term reliablity of optical fiber connections. It required a gauge retention force Fr of more than 200 gf to suppress the fluctuation in the insertion loss of a plastic sleeve. From the fluctuation data, we estimated the time-to-failure tf at which the Fr value became 200 gf. We estimated the acceleration parameters, median lifetimes ξ, and hazard rates λ by using the tf values based on the Weibull statistics. The ξ values decreased rapidly with increasing temperature and relative humidity. Small λ values of < 0.01 FITs and of 1 FITs were expected for 20 years in a normal atmosphere (25C/50%RH) and in a more severe case of 25C/90%RH or 45C/50%RH.

Plastic ferrules for single-mode (SM) MU-type simplified receptacles are fabricated with a precise injection-molding technique using a liquid crystalline polymer (LCP). The fabricated plastic ferrules exhibit an eccentricity of < 0.6 µm and outer diameter variation of 1 µm. MU-type simplified plugs incorporating the plastic ferrules have an average insertion loss of 0.13 dB and a return loss of > 46 dB. The plastic ferrules exhibit good resistance in 500-cycle mating tests, and in vibration and impact tests as well. The initial optical characteristics are maintained during a temperature and humidity cycling test and a heat-cycling test.