Electrical filter-based and low-complexity DPSK coherent optical receiver

Area of Science:

• Optical communications
• Signal processing
• Photonics

Background:

• Direct detection of differential phase shifted keying (DPSK) optical signals traditionally relies on optical filtering or interferometers.
• Limitations exist with optical filters, especially for ultra-narrow bandwidth requirements like in ultra-dense wavelength division multiplexing (WDM) passive optical networks.

Purpose of the Study:

• To introduce and demonstrate a coherent receiver that performs filtering in the electrical domain after down-conversion.
• To highlight the advantages of electrical domain filtering for DPSK signal detection, particularly in scenarios where optical filters are impractical.

Main Methods:

• Down-converting the incoming DPSK optical signal to baseband or intermediate frequency.
• Implementing filtering in the electrical domain using electrical filters.
• Experimentally demonstrating the proposed reduced complexity receiver and comparing its performance to a classical 'delay and multiply' receiver.

Main Results:

• Electrical domain filtering is shown to be a viable and advantageous alternative to optical filtering for DPSK signals.
• The proposed method is colorless and avoids complex digital signal processing.
• Experimental validation confirms the feasibility and benefits of the reduced complexity receiver.

Conclusions:

• Electrical domain filtering in a coherent receiver offers a more accurate and flexible approach for DPSK signal detection.
• This technique is particularly beneficial for advanced optical networks requiring narrow filtering, such as ultra-dense WDM systems.
• The demonstrated receiver design simplifies optical communication systems by reducing complexity and avoiding digital signal processing.