High-sensitivity DPSK receiver for high-bandwidth free-space optical communication links.

Area of Science:

• Optical Engineering
• Telecommunications
• Signal Processing

Background:

• Free-space optical (FSO) links face challenges due to dynamic environmental conditions, impacting signal stability and link margin.
• Achieving high data rates over FSO links requires robust components capable of handling signal fluctuations and noise.
• Existing technologies may struggle to provide the necessary sensitivity and dynamic range for demanding FSO applications.

Purpose of the Study:

• To develop a high-sensitivity modem and a high-dynamic range optical automatic gain controller (OAGC) for FSO communication.
• To maximize link margin and effectively manage the dynamic nature of FSO links.
• To achieve high data rates with improved signal integrity in free-space optical systems.

Main Methods:

• A return-to-zero differential phase shift keying (RZ-DPSK) modem was employed for high-sensitivity data transmission.
• A commercial Reed-Solomon forward error correction (FEC) system was integrated to enhance data reliability.
• A low-noise optical automatic gain controller (OAGC) with a wide dynamic range was utilized to manage signal power.

Main Results:

• A modem sensitivity of -48.9 dBm (equivalent to 10 photons per bit) at 10 Gbps was demonstrated.
• The OAGC provided low-noise optical gain with a noise figure of 4.1 dB.
• The OAGC exhibited a dynamic range exceeding 60 dB, crucial for variable link conditions.

Conclusions:

• The developed high-sensitivity modem and OAGC significantly improve performance in free-space optical links.
• These components enable maximum link margin and overcome the dynamic nature of FSO communication.
• The achieved sensitivity and dynamic range pave the way for more robust and reliable FSO communication systems.