Low-complexity turbulence resilience enabled by a multi-mode bi-directional transceiver

Area of Science:

• Optical Communications
• Fiber Optics
• Free-Space Optics

Background:

• Free-space optical (FSO) systems face challenges from mechanical instability and atmospheric turbulence, causing distortions and high losses.
• These issues typically necessitate adaptive optics for single-mode bi-directional systems, limiting practical deployment.
• Multi-mode fibers offer potential advantages in mitigating these FSO communication challenges.

Purpose of the Study:

• To investigate and compare the performance of step and graded index multi-mode fibers for bi-directional FSO communication.
• To evaluate the suitability of OM5 graded index fiber for FSO applications, specifically its field of view and transmission mode characteristics.
• To demonstrate high-speed, error-free FSO communication using OM5 fiber without adaptive optics.

Main Methods:

• Emulation of a 400m FSO channel.
• Performance comparison of step-index and graded-index multi-mode fibers.
• Utilizing commercial bi-directional small form-factor pluggable (SFP+) transceivers.
• Testing under varying turbulence conditions (D/r0 = 3 and D/r0 = 9).

Main Results:

• OM5 graded index fiber provides a near-Gaussian optical transmission mode.
• OM5 fiber offers a >5x increase in field of view compared to single-mode fiber.
• Error-free throughput of 10 Gbps achieved under low turbulence (D/r0 = 3).
• Error-free throughput of 9.1 Gbps achieved under high turbulence (D/r0 = 9).

Conclusions:

• OM5 graded index fiber can support high-speed bi-directional FSO communication.
• The use of OM5 fiber eliminates the need for adaptive optics in FSO systems.
• OM5 fiber presents a viable solution for robust FSO communication systems facing environmental challenges.