This Small Business Technology Transfer (STTR) Phase II project will develop a novel optical fiber sensor of temperature, pressure, extension, axial twist and various environmental factors, including liquid level, in harsh environments. The optical fiber sensor will be free of electromagnetic interference and of the hazard of igniting combustible fuels and will be capable of remotely monitoring temperatures up to and beyond 750 °C and of tolerating high-radiation levels. Conventional long period gratings fiber (LPGs) formed by exposing photosensitive doped optical fibers to patterned ultraviolet illumination cannot operate in harsh environments because of the fragility of the imprinted periodic structure. In contrast, the glass fiber in the dual-twist chiral fiber sensor (CFS) need not be photosensitive and will be chosen for its robustness. The chiral long-period grating (CLPG) structure of the CFS will be created in a glass-forming process in which signal and scaffolding optical fibers are twisted together to form a helix in the signal fiber as the fibers pass through a miniature oven. Transmission dips due to coupling of the light between the core and surrounding glass cladding by the chiral grating and their shift with environmental factors will be measured and calculated using an increasingly sophisticated sequence of perturbation theories.
The CFS based on the dual-twist CLPG structure overcomes the disadvantages of the LPG and of the CFS based on twisting single birefringent fibers. If successful it is ideally suited for demanding applications such as found in nuclear reactors, outer space, and oil wells, as well as in medical diagnostics and treatment and in the automotive and aerospace industries. The CFS may therefore become a pervasive part of modern technology and everyday life which relies increasingly on sensing and automated decision making. By substantially raising the operation temperature of optical fiber sensors, substantial savings can be realized. Conventional power generators could run at higher temperatures where they are substantially more efficient and the recovery rate in oil reservoirs can be increased considerably. The use of high-temperature and radiation-resistant CFSs in nuclear power plants can make these facilities more efficient and safe. The enhanced range of conditions in which the CFS can function relative to conventional electrical and optical sensors will have an impact across the economy and will make the CFS a rapidly growing segment of the multi-billion dollar sensor market. The novel glass forming fabrication methods and computational approaches may find use in diverse fields including photonics, microfluidics and medical diagnostics.
In Phase II of this Small Business Technology Transfer (STTR) award, Chiral Photonics, Inc. (CPI) developed and brought to market a number of fiber optic components, including: An ultra-high temperature fiber optic temperature sensor that can operate with high accuracy up to 1000 degrees Celcius (Figure 1). Along with fiber optic stability, electromagnetic immunity and remote operation, this extends to harsh environment applications, such as oil refinery and turbine engine monitoring and control. Enabling multicore fiber fanouts (Figure 2). These high density couplers enable addressing of increasingly dense independent channels within optical fiber. Multicore fiber is increasingly applied to communications, for reducing size and energy expenditure while increasing bandwidth, but is also playing a pivotal role in shape sensing, extremely sensitive positional sensing that can track the exact location and orientation of a tiny fiber via the signals carried in its individual channels. This technology is being applied to, for example, minimally invasive surgery for finer control, adaptive wind turbines and airplane jets to improve energy efficiency and performance and structural health monitoring. A highly compact optical switch (Figure 3) that can be used for applications ranging from highly multiplexed sensing systems to more energy efficient data centers straining to keep up with burgeoning bandwidth needs. Optically enabled endoscopy probes that promise less invasive cancer diagnostics and treatment. These fiber-based innovations build on Chiral Photonics’ simulation, fiber design and microforming process capabilities which involve twisting, shaping and splicing of fiber with submicron precision to deliver new and enabling functionality. Development of these components have broader implications to photonic integrated circuit packaging where dense coupling is a vexing issue holding back wider adoption. Optogenetics and other biomedical fields will benefit from instruments that can integrate photonic and microfluidic functionality, readily extendable goals given the multichannel structures demonstrated here. Published and presented work on these fiber optic components, as well as engagement with undergraduate and graduate students, continues to expand and disseminate understanding of the photonics and engineering involved. Production capabilities and innovations inform design, a creative avenue often not possible in fabless operations, where the creativity primarily flows from design to fabrication. This may shed some light on more subtle, longer view, advantages of more vertically integrated business structures.
