Pingping Fu

Design and demonstration of single-mode operation in few-mode optical fiber with low-bending loss

Abstract. Single-mode operation with low-bending loss based on few-mode optical fiber is investigated. The fiber is designed with a group of ring modes in the cladding. The higher-order modes in the fiber can be eliminated by splicing with the single-mode optical fiber and bending the fiber to induce a strong coupling between the ring modes and the higher-order modes. Experimental results show that the bending losses of the LP01 mode can be lower than 0.001  dB/turn for a low-bending radius of 7.5 mm. The low-bending loss and the low splicing loss characteristics are also demonstrated. The proposed fiber can be bent multiple turns with a small bending radius which is preferable for fiber-to-the-home-related applications.

Single-mode operation in few-mode optical fibre based on resonant coupling

Abstract The design of a low-bending loss few-mode optical fibre is proposed. Low-bending loss for the fundamental mode is achieved by increasing the index contrast between the core and the cladding, and a microstructured mode filtering region is applied to filter out the higher-order modes in the fibre. Numerical results show that the fundamental mode loss is lower than 0.03 dB/turn and the high-order mode is higher than 4.4 dB/turn at the bending radius of 5 mm and 1300–1600 nm wavelength range.

Research of a single-polarization suspended-core micro-structured fiber

Single-polarization single-mode (SPSM) fibers, supporting only one polarization state within some particular wavelength ranges, can suppress both polarization mode couplings and polarization mode dispersions, which have extensive applications in various techniques such as fiber optic gyroscopes, high power fiber lasers, current sensors, and other polarization-sensitive components. The suspended-core PCF, based on index-guiding mechanism, is one promising kind of fiber which can easily realize single-mode operation and meanwhile keep a relatively larger fraction of the guided mode power distributing in the air. This type of fiber, due to the property of the high overlap factor of the evanescence field, has attractive applications in chemical or biological sensing and gas sensing areas. In this paper we present the design and investigation of a single-polarization suspended-core fiber with an elliptical core consisting of crossed rectangular shaped dielectric strips. A rectangular shaped dielectric strip distributes in an orientation which has an angle θ with the x-axis, and the other strip distributes in the direction which has an angle π-θ with the x-axis. The two strips have the same thickness and width with each other. The intersection part of the two strips acts as the fiber core. The rest of these rectangular shaped strips and four big air holes constitute the cladding of the fiber. The guiding mechanism of the proposed fiber is the total internal reflection. By adjusting the fiber structure parameters, one polarized mode can be effectively eliminated through certain transmission distance and the single-polarization operating can be realized. For some cases with optimized fiber configuration parameters, single-polarization single-mode transmission with broad bandwidth can also be obtained. Meanwhile, the power fraction within air of the x-polarization mode for this fiber is relatively high which facilitates its applications in high precision sensors.