Wavelength multiplexed quadrature amplitude modulation for low cost high capacity data transmission over plastic optical fibre

Since the bandwidth of large-core step-index polymer optical fiber is quite limited, Quadrature Amplitude Modulation is considered to increase the channel capacity. Using two low cost LEDs, at 460nm and 650nm respectively, the in-phase and quadrature-phase signals of the QAM signal are transmitted in two different wavelength channels. In the transmitter the two optical signals were combined with a plastic optical fibre splitter. At the receiving end plastic optical fibre filters were used to separate the blue and red optical signal. The performance of the system has been measured using a vector signal analyser. Using 16 QAM, 60 Mbit/s over 100 m 1 mm core diameter step-index PMMA optical fiber has been realized. This system showed the feasibility of QAM transmission for low-cost high-speed transmission over large core plastic optical fibre. Using higher order QAM transmission and/or using a 650nm red LED with a higher bandwidth, the transmission capacity can be increased further