Wavelength reuse in a bidirectional UWB over fiber system

Area of Science:

• Optical Communications
• Photonics
• Signal Processing

Background:

• Bidirectional ultra-wideband (UWB) over fiber systems face challenges with downstream signal interference impacting upstream transmission.
• Phase-modulation to intensity-modulation (PM-IM) conversion is a primary source of crosstalk in such systems.
• Efficient wavelength reuse is crucial for increasing spectral efficiency in optical networks.

Purpose of the Study:

• To propose and experimentally demonstrate a novel wavelength reuse scheme for bidirectional UWB over fiber systems.
• To eliminate the impact of downstream signals on upstream transmission by canceling PM-IM conversion.
• To achieve high-performance, error-free data transmission in a shared wavelength scenario.

Main Methods:

• Utilizing a polarization modulator (PolM) for phase modulation along orthogonal axes with opposite indices.
• Employing an electro-absorption modulator (EAM), a polarization-independent component, for signal modulation.
• Implementing a system design where complementary PM-IM signals cancel each other out in the upstream link.
• Experimentally transmitting a 1.25-Gbps UWB signal over 17 km of single-mode fiber (SMF).

Main Results:

• Successful demonstration of error-free bidirectional transmission of a 1.25-Gbps UWB signal.
• Complete elimination of downstream signal interference on upstream transmission due to PM-IM cancellation.
• A minimal power penalty of only 0.2 dB was measured for upstream transmission with wavelength reuse.

Conclusions:

• The proposed method effectively enables wavelength reuse in bidirectional UWB over fiber systems.
• The complementary cancellation of PM-IM conversion by the PolM and EAM is a robust solution for crosstalk.
• This technique offers a promising approach for enhancing spectral efficiency and performance in optical communication systems.