The feasibility of wavelength division multiplexing 800, 1300 and 1500 nm channels over an 8 km long, installed, 1300nm optimised single-mode fibre loop has been demonstrated. A 780 nm CD-laser and Si-APD receiver were used to transmit data at 150 Mbit/s on one of the channels. A 0.25 metre long, 800 nm optimised SM fibre section was used at the receiver to filter the LP11 mode propagating in 1300 nm optimised SM fibre at 800 nm. The mode filter significantly reduced intermodal distortion, thus allowing high-speed 800 nm transmission over the loop. Edge-emitting, 1300 and 1500 nm LEDs were used to transmit 140 and 90 Mbit/s data, respectively.