We present characteristics of very thin Au strip waveguides based on long-range surface plasmon polaritons (LR-SPPs) along thin Au strips embedded in polymers. We also report a 10 Gbps optical signal transmission via LR-SPPs with the pig-tailed Au strip waveguide at a telecommunication wavelength of 1.55 mum. We limited the thickness, width, and length up to ~20 nm, ~ 10 mum, and ~5 cm, respectively, for practical applications. At 1.55 mum, loss properties of the Au strip waveguides were theoretically and experimentally evaluated with thickness, width and cladding material. The lowest propagation loss of ~1.4 dB/cm was experimentally obtained with the 14-nm-thick and 2-mum-wide Au strip. With a single-mode fiber, the lowest coupling loss of less than 0.1 dB/facet was achieved with the 14-nm-thick and 7.5-mum-wide Au strip. The lowest insertion loss was obtained 7.7 dB with the 14-nm-thick, 5-mum-wide, and 1.5-cm-long Au strip. The propagation loss was improved approximately 30% for the 17-nm-thick Au strip with lowering the refractive index of the cladding polymer by 0.01. In the 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10-12 bit error rate. These all results indicate that the LR-SPP waveguide is a potential transmission line for optical interconnects to overcome inherent problems in electric interconnects.