Recently it has been shown that standard single-mode fibers, which support two LP modes around 850 nm, can yield high modal bandwidth with graded-index profile design. A transmission system using such fibers along with 850 nm single mode VCSEL transceivers offers a potentially cost-effective high-bandwidth solution for data center applications and future high-speed short distance communications. The system reach highly depends on the modal bandwidth of the fiber. In this context, it is of interest to explore the characterization method of the modal bandwidth of two-mode and few-mode fibers, especially if the method can be simpler than traditional methods used for 50-μm core multimode fiber. To address this issue, we propose a simple and robust method for two-mode and few-mode fiber modal delay and bandwidth measurements using frequency domain method. An analytical transfer function model was formulated and achieved excellent agreement with experimental results. The model allows one to extract the modal delay based on one single measurement, regardless of the launch condition. The transfer function and hence modal bandwidth with arbitrary launch condition can be calculated, from which we define a worst-case modal bandwidth that can gauge the fiber modal bandwidth under general conditions. The analytical model is also generalized to consider higher-order modes and additional bandwidth degradation effects. Through the detailed study, we show that the simple frequency domain measurement method as facilitated by the analytical model can deliver a full set of modal delay and modal bandwidth information that otherwise requires more complex method like differential mode delay measurements.
The use of a rectangular core fiber is suggested for mode division multiplexed optical communication, and as an alternative fiber geometry having advantageous transmission and component integration attributes. The rectangular core is constrained to support single transverse modes in one direction and multiple modes in the horizontal transverse direction. The supported modes are thus polarization degenerate only (i.e., TE1x and TM1x), with well separated momenta and favorable mode profiles for device coupling and wavelength multiplexing and manipulation. A fiber prototype is experimentally characterized for its modal delays and field profiles by time-gated interferogram analysis.
In this paper, we present an optical fiber that is single-mode at 1310 nm window and few-mode at 850 nm window with high bandwidth. The fiber is compatible with standard single-mode fiber at 1310 nm, which can meet long reach requirements for hyper-scale data centers. In addition, the fiber can be used for few-mode transmission at 850 nm using single-mode or few-mode VCSELs, providing low-cost solutions for short links. We discuss fiber design considerations and present fiber properties and 25 Gb/s transmission results at 850 nm.
In this paper, we propose bend insensitive fiber designs that can meet both the bend loss and mechanical reliability needs for silicon photonic packaging. To improve the bend loss, we adopt profile designs with a low index trench that allow us to reduce the bending loss while keeping the mode field diameter compatible with the standard single mode fiber. To improve the mechanical reliability, we put a Titania-doped glass layer on the surface of the fiber cladding, which improves the fiber reliability under tight bending conditions. We describe both the core and Titania layer designs and present results on fiber optical and mechanical performances.
We present novel optical fiber designs to improve performance of distributed optical fiber sensors based on Rayleigh and Brillouin scatterings, including hybrid core fiber for increasing Rayleigh backscattered signal, dual core fiber for simultaneous measurement of temperature and stain, few mode fiber for enhancing sensitivity and spatial resolution and Brillouin frequency managed fiber for increasing sensing range.
In this paper, we present a new type of optical fiber, called universal fiber, which can be used for both multimode and single mode transmissions. The fiber is a multimode fiber that has an LP01 mode field diameter approximately matched to that of standard single mode fiber. First, we will present the universal fiber design concept and discuss design tradeoffs for both single mode and multimode operations. Then we will show characterizations of a preliminary experimental fiber and present system testing results with 110 m, 150 m and 2700 m system reach using 100G SR4, 40G sWDM multimode and 100G CWDM4 single mode transceivers, respectively, which demonstrate both multimode and single mode transmission capabilities of universal fiber.