Practical Evaluation of Polymer Waveguides for High-Speed and Meter-Scale On-Board Optical Interconnects

Abstract

We comprehensively evaluated optical characteristics, environmental stabilities, fiber optics compatibilities, and high-speed performances of multimode polymer waveguides fabricated in small batch with a length of 946 mm. The waveguides exhibit a low transmission loss (0.046 dB/cm at a wavelength of 850 nm), low interchannel crosstalk (≤ −58 dB), and a large misalignment tolerance (±20 μm) between fiber and waveguide. The waveguides show good environmental stability and the increase of propagation loss is as small as 0.005 dB/cm and 0.004 dB/cm after a 1000-h ageing test and five solder reflow cycles, respectively. The waveguides have good compatibilities with fibers having different core diameters and index profiles that may be encountered in the real application environment. High-speed transmission performances were evaluated using both nonreturn to zero (NRZ) transmission at data rates of 25 Gb/s and 30 Gb/s, and PAM4 transmission at data rates of 20 Gb/s and 56 Gb/s, respectively. There is no obvious degradation on the eye diagram due to the insertion of the waveguide. Error free transmission were successfully obtained for NRZ transmission at data rates of both 25 Gb/s and 30 Gb/s. The BER for PAM4 transmission reached a level of 10−4 at data rates of both 10 Gbaud (20 Gb/s) and 28 Gbaud (56 Gb/s), which is well below the forward error correction limitation. Moreover, it is the bandwidth of the test equipment rather than the polymer waveguide itself that limits the high-speed transmission performances in our experiments. The results demonstrate that the polymer waveguides are good candidates for high-speed and meter-scale on-board optical interconnect applications.