Fiber Optic Damage Assessment System

Sponsored by: Office of Naval Research

AITHER is developing a fiber optic damage assessment system (FODAS) based fiber Bragg grating (FBG) technology for monitoring damage to Navy ships. The implementation of an automated network of ship condition sensors will have a number of direct benefits that will increase ship and crew survivability during a ship damage event. The automated damage sensor network concept would reduce the need for in-person investigations of alarm events in individual compartments, allowing for reduced crew manning of ships. The reduced manning will reduce the number of U.S. personnel killed or injured by attacks on U.S. Navy ships. By eliminating in-person investigation of alarm events, the ship’s damage assessment personnel will quickly have a complete picture of the ship’s condition, thus increasing the likelihood of surviving and recovering from the attack in less time and with less overall damage. The automated assessment of the ship’s condition will also improve the operational readiness of U.S. Navy forces. The realization of reduced manning in U.S. Navy ships will reduce the overall operations and support (O&S) costs for the fleet.

The focus of the Phase I SBIR effort was the demonstration of the basic components necessary for the FODAS concept based on FBG technology. AITHER designed damage control sensors based on FBG sensor technology to detect shipboard fires, flooding, and door closure status. AITHER tested and demonstrated the basic measurement principles behind each sensor. We demonstrated the ability of the FBG high-range temperature sensors to linearly measure temperature up to 650°F (343°C), and we tested sensors to above 700°F (371.1°C) where the adhesive failed. Alternative adhesives and integration techniques were identified that can extend the temperature measurement capability to above 1000°F (538°C). AITHER designed a flooding sensor, and prototyped and tested the flooding (pressure) sensing design that contains no moving parts. This sensor demonstrated good repeatability and linearity in laboratory testing. AITHER designed and tested a FBG-based door status sensor to detect the state of critical compartment doors. The sensor was built and tested and demonstrated that the design provided three unique and constant strain levels depending on the sensor plunger position, which correlates to door status.

The instrumentation system used in the FODAS concept to interrogate the FBG sensors was developed by AITHER under a previous SBIR program. During the Phase I phase of the FODAS program, AITHER examined the feasibility of increasing the channel density of the High Speed – Fiber Optic Interrogation System (HS-FOIS) hardware from 8 optical channels to 48 optical channels. AITHER purchased a 48-channel fiber array and examined the adjacent channel cross talk, sensor noise, and power requirements for a 48-channel HS-FOIS. AITHER determined that extending the current HS-FOIS technology to monitor 48 optical channels simultaneously does not pose any significant technical risks and requires updated but readily available commercial optical components.

The recently awarded Phase II FODAS program will focus on refining the design and manufacturing the FBG-based damage control sensors for shipboard use and modifying the HS-FOIS base software for monitoring and reporting damage control sensor readings in a network architecture. The full FODAS system will then be installed on instrument test compartments aboard the ex-USS Shadwell for a series of damage control tests. The FODAS sensor and interrogation system technology will be used to monitor compartment temperatures, flooding, and door/hatch status during damage control testing aboard the ex-USS Shadwell.