Abstract
We demonstrate the 40-Gb/s upstream transmission in the 60-km reach wavelength-division-multiplexed passive optical network (WDM PON) implemented by using directly modulated reflective semiconductor optical amplifiers (RSOAs) and self-homodyne receivers. It is difficult to operate the RSOA at 40 Gb/s due to its limited modulation bandwidth. To overcome this problem and generate 40-Gb/s upstream signal, we utilize the quadrature phase-shift-keying (QPSK) format and the offset polarization-division-multiplexing (PDM) technique. For this purpose, we install two RSOAs at each ONU and provide the seed light for these RSOAs by polarization-multiplexing the outputs of two lasers with a small frequency offset (20 GHz). This frequency offset is used to separate the polarization-multiplexed seed light by using a simple delay-line interferometer (DLI), instead of the polarization-beam splitter and polarization controller, at the ONU. The separated seed light is modulated by each RSOA at 20 Gb/s in the QPSK format, and then combined again by the DLI before sent back to the central office (CO). The results show that this WDM PON can support the transmission of 40-Gb/s channels spaced at 50 GHz over 60 km without using any remote optical amplifiers.
Highlights
To meet the ever-increasing demand for bandwidth, it will be necessary to develop the highspeed optical access network capable of providing >40-Gb/s service to each subscriber in the near future [1,2]
We demonstrate the 40-Gb/s upstream transmission in the 60-km reach wavelength-division-multiplexed passive optical network (WDM PON) implemented by using directly modulated reflective semiconductor optical amplifiers (RSOAs) and self-homodyne receivers
It is difficult to operate the RSOA at 40 Gb/s due to its limited modulation bandwidth
Summary
To meet the ever-increasing demand for bandwidth, it will be necessary to develop the highspeed optical access network capable of providing >40-Gb/s service to each subscriber in the near future [1,2]. To generate the 40-Gb/s upstream signal by using the RSOAs having a limited modulation bandwidth of only ~3.2 GHz, we utilize the quadrature phase-shift-keying (QPSK) format and the offset polarization-division-multiplexing (PDM) technique [6,7,8]. For this purpose, we multiplex the outputs of two seed light sources, operating with a small frequency offset (20 GHz), by using a polarization-beam splitter (PBS), and send to the ONU. The results show that 40-Gb/s WDM PON with the maximum reach of 60 km can be realized cost-effectively by using the proposed techniques
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