Thermal treatment effect on the performance of fused polymer optical fiber coupler device

A weakly fused (WF) and a highly fused (HF) polymer optical fiber (POF) star coupler based on fusing and combining a group of POFs are successfully designed and experimentally investigated. The sleeve removed group of POFs are fused together using a Bunsen burner with a yellow flame. Variation of temperature were applied directly to the fused tapered region and an LED fiber source with a 650 nm wavelength is launched into the fiber input, while the optical power deviation is measured at each output port. The new fusion technique 3×3 couplers were developed. The coupling ratio (CR) and return optical power (ROP) and its effect to the temperature variation of 20 0C to 125 0C were also investigated. The result shows the excess loss, EL0 for the WF and the HF coupler at 20 °C is ~ 2 dB and ~ 8 dB, respectively. This paper aims to examine the feasibility of both methods of 3×3 POF couplers as thermal optical switches and also to determine whether the thermal treatment is needed to improve the performance and able to shift the device specification (if possible). Finally, the results reveal the thermal treatment (approximately 10 °C above room temperature) could improve the device performance by reducing the reflected power and contribute to minor shifting to the coupling ratio. Thus, the specification of the device can be adjusted according to the requirement.