The use of optical fibers in low earth orbiting (LEO) satellites is a source of concern due to the radiation environment in which these satellites operate and the reliability of devices based on these fibers. Although radiation induced damage in optical fibers cannot be avoided, it can certainly be minimized by intelligent engineering. Qualifying fibers for use in space is both time consuming and expensive, and manufacturers of satellites and their payloads have started to ask for radiation performance data from optical fiber vendors. Over time, Nufern has developed fiber designs, compositions and processes to make radiation hard fibers. Radiation performance data of a variety of fibers that find application in space radiation environment are presented.
The need for precision guidance of systems in tactical theaters is becoming increasingly more important. This need has renewed interest in Interferometric Fiber Optic Gyroscopes (IFOG) that are capable of delivering navigation grade performance. The challenges however, include satisfactory performance over a large and severe operating temperature range (-60°C to +90°C), low unit cost and relatively small footprint. Performance of the IFOG depends critically on the quality of the sensing element, optical fiber coil, and many of the performance limiting issues of the IFOG can be traced back to coil quality. Although significant progress has been made in the fabrication of temperature insensitive coils with high optical reciprocity, more needs to be done. In this paper, data is presented on the performance of similar size (inside diameter, outside diameter, height) freestanding coils that were wound in quadrupole winding pattern at low tension using different polarization maintaining fibers. Performance characteristics of the coils were measured under variables including (i) fiber geometry, (ii) fiber coating, (iii) winding epoxy, and (iv) epoxy curing profile. Although each coil had the same footprint, they contained different lengths of fiber based on the fiber coating size. Coils were characterized as a function of temperature with respect to: (i) optical loss, (ii) polarization extinction ratio (PER), and (iii) coherence. The data suggests that high performance navigation grade coils can be realized over a large and severe temperature range with careful choice of fiber, winding epoxy and cure cycle.
A microelectromechanical system (MEMS) device might function perfectly well in the controlled environment in which it has been created. However, the device can be a real viable product only after it has been fabricated with proven performance in a package. As such, the assembly yield of a MEMS package is often a challenging target to meet. The design and fabrication of a free-floating membrane on a flexible substrate to enable easy and cost-effective packaging of MEMS devices is examined. Since standard MEMS fabrication processes are designed for rigid substrates, several process modifications were required to handle flexible substrates. The adaptation of each fabrication process has been documented. Furthermore, detailed information regarding the selection of compatible materials, as well as incompatibilities that were encountered, has been presented to aid future researchers in developing processes for flexible substrates.
Monolithic, all-fiber PM optical amplifiers have been investigated regarding components performance,
amplifier design and narrow line-width amplification. PM-based components performed very well, the
pump/signal combiner in particular handling > 300W pump power and still maintaining the PER of the
input signal. A co-pumped amplifier configuration was chosen based on reliability and potential SBS
mitigation (i.e. fiber length after the active fiber output). This system based on PLMA-YDF - 25/400 fiber
appeared to give the best output power (155W-177W, depending on the length of passive delivery fiber),
PER (~ 17 dB) and excellent beam quality (M2= 1.1). Altering the fiber temperature and length were
necessary to provide the best results.
Being the new frontier of science and technology, as the near earth space begins to attract attention, low cost and rapidly
deployable earth observation satellites are becoming more important. Among other things these satellites are expected
to carry out missions in the general areas of science and technology, remote sensing, national defense and
telecommunications. Except for critical missions, constraints of time and money practically mandate the use of
commercial-off-the-shelf (COTS) components as the only viable option. The near earth space environment (~50-50000
miles) is relatively hostile and among other things components/devices/systems are exposed to ionizing radiation.
Photonic devices/systems are and will continue to be an integral part of satellites and their payloads. The ability of such
devices/systems to withstand ionizing radiation is of extreme importance. Qualification of such devices/systems is time
consuming and very expensive. As a result, manufacturers of satellites and their payloads have started to ask for
radiation performance data on components from the individual vendors. As an independent manufacturer of both
passive and active specialty silica optical fibers, Nufern is beginning to address this issue. Over the years, Nufern has
developed fiber designs, compositions and processes to make radiation hard fibers. Radiation performance data (both
gamma and proton) of a variety of singlemode (SM), multimode (MM), polarization maintaining (PM) and rare-earth
doped (RED) fibers that find applications in space environment are presented.
For intrinsic fiber optic sensors such as interferometric fiber optic gyroscopes that use polarization maintaining fibers, performance of the fibers that constitute the sensing coils is a key issue. In general, requirements include small form-factor, good bend performance, tight tolerances on fiber geometry and ability to maintain a single polarization state. Currently, bow-tie or elliptical clad type high birefringence fibers are used in such sensors. This paper deals with the development and characterization of small form-factor (80 μm) PANDA style high birefringence fibers for sensing applications at different wavelengths of interest. The rationale and advantages of the new design are discussed along with geometrical and optical characteristics of one new fiber. Performance data of the fiber in terms of cross-talk variation in the -55 to + 85°C temperature range are presented.