This paper demonstrate a large-size directly inscribed optical waveguide for card-to-card optical interconnects applications. The waveguide was fabricated with commercially available UV-curable epoxies by combining use of a needle-type liquid micro-dispenser and a 3-axis robot stage known as the mosquito method. We designed and fabricated an “E” shaped waveguide device with 3 input/output ports and three connection routes with a length of about 21 cm, 21 cm, and 27 cm, respectively, to fit card-to-card connections of the optical backplane. The optical layout was designed to be scalable for conventional backplane sizes. Moreover, both the optical and geometrical parameters of the waveguides are designed to be compatible with commercial devices and can be terminated with MT connectors. The measurement results show good optical performance in insertion loss, crosstalk, misalignment tolerance, and good uniformity for all the 18 channels. The average insertion loss of the 27 cm-long channels is about 4.5 dB and the misalignment tolerance is larger than 20 μm for 3 dB loss penalty. The measured inter-channel waveguide crosstalk is lower than 42 dB. The waveguides also show excellent high-speed transmission performances with a NRZ signal at a data rate of 32 Gb/s. The experimental results imply that the large-size directly inscribed circular core polymer waveguide device is suitable for card-to-card optical interconnects applications and especially useful and versatile for the development of the porotype systems.