High-Bandwidth Multimode Fiber-Optic Cabling

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Integrated Network Systems-of-Systems; Microelectronics; Sustainment OBJECTIVE: Design and develop a high-bandwidth multimode optical fiber for avionic and sensor applications. DESCRIPTION: Current airborne military (mil-aero) core avionics, electro-optic (EO), communications, and electronic warfare systems require ever-increasing bandwidths while simultaneously demanding reductions in space, weight, and power (SWaP). The replacement of shielded twisted pair wire and coaxial cable with earlier generation, bandwidth-length product, multimode optical fiber has given increased immunity to electromagnetic interference, bandwidth, and throughput, and a reduction in size and weight on aircraft. The effectiveness of these systems hinges on optical communication components that realize high-per-lane throughput, low-latency, and large link budget, and are compatible with the harsh avionic environment. In the future, data transmission rates of 100 Gbps and higher will be required. Substantial work has been done to realize data rates approaching this goal based on the use of multilevel signal coding, but multilevel signal encoding techniques trade off link budget and latency to achieve high-digital bandwidth. To be successful in the avionic application, existing non-return-to-zero (NRZ) signal coding with large link budget and low-latency must be maintained. There has been considerable focus on the transmitters and receivers for future optical interconnects, but limited attention to optimizing the fiber cabling. Current aircraft have a mix of fiber types that were not anticipated for such high-speed operation. Multimode optical fiber is strongly preferred over single mode optical fiber given the environmental and operating conditions. To further future proof the embedded optical cabling, the Navy seeks a new class of multimode optical fiber that can support operation of 100 Gbps and higher NRZ while maintaining efficient coupling to the optical transmitters and receivers and compatibility with military style fiber-optic termini. The proposed optical cabling must operate across a -55 C to +165 C temperature range, and maintain performance upon exposure to typical naval air platform vibration, humidity, temperature, altitude, thermal shock, mechanical shock, and temperature cycling environments. The optical fiber must be compatible with lasers in the 850 to 1500 nm band operating at 100 Gbps and higher NRZ to support bandwidth in excess 10 GHz*km. Optical attenuation loss should be consistent with current OM5 multimode fiber. PHASE I: Design a multimode optical fiber with bandwidth > 10 GHz*km that is compatible with lasers in the S band (850 to 1050 nm) and the O-band (1260 nm to 1400 nm). Develop differential mode dispersion measurement techniques to profile the optical fiber in both the S and O band. The Phase I effort will include prototype plans to be developed under Phase II. PHASE II: Optimize the fiber for high-speed operation over temperature. Measure and define specific launch conditions needed to maintain the bandwidth. Characterize link error potential as a function of connector misalignment, transmitter and receiver optical subassembly design, and environmental conditions. PHASE III DUAL USE APPLICATIONS: Support transition of the technology to military aircraft platforms. Commercial datacenters will be able to use this new fiber optic cable to connect routers and servers. REFERENCES: IEEE 802.3 Ethernet Working Group. (2023). IEEE 802.3. IEEE. https://www.ieee802.org/3/ Telecommunications Industry Association (TIA). (2009). TIA-455-203, Revision A: FOTP-203 Light source encircled flux measurement method. https://global.ihs.com/doc_detail.cfm?item_s_key=00334007&item_key_date=850612&rid=GS Telecommunications Industry Association (TIA). (2003). TIA-455-220: FOTP-220 Differential mode delay measurement of multimode fiber in the time domain. https://global.ihs.com/doc_detail.cfm?item_s_key=00388929&item_key_date=961131&rid=GS International Electrotechnical Commission. (2019). IEC 60793-2-10 (2019). Optical fibres Part 2 10: Product specifications Sectional specification for category A1 multimode fibres. International Electrotechnical Commission (IEC), 7th Edition. https://webstore.iec.ch/publication/62020 Telecommunications Industry Association (TIA). (2009). TIA-492AAAD: Detail Specification for 850-nm laser-optimized, 50 m core diameter/125- m cladding diameter class Ia graded-index multimode optical fibers suitable for manufacturing OM4 cabled optical fiber. https://standards.globalspec.com/std/1194330/TIA-492AAAD KEYWORDS: non-return-to-zero (NRZ); multimode fiber; 10 GHz*km; launch condition; the S band (850 to 1050 nm) and the O-band (1260 nm to 1400 nm); fiber optic cable.