Vincent J. Tekippe

Fiber-optic diaphragm-curvature pressure transducer.

A novel fiber-optic sensor that determines pressure from diaphragm curvature is discussed. This sensing technique exhibits a high degree of sensitivity and linearity and is less susceptible to environmental perturbations than previous intensity-modulating techniques. Experimental results are presented for a miniature pressure transducer suitable for in vivo medical applications.

Production, performance, and reliability of fused couplers

It has been twenty years since the first fused fiber optic coupler was made and remarkable progress has been achieved during this period on the production, performance, and reliability of these devices. Several million fused couplers have now been produced and placed into service. Applications have included test instrumentation, both outside plant and central office telephony applications, cable TV systems, sensors, optical amplifiers, DWDM systems, and submarine repeaters, to mention a few. To meet the increased production requirements, significant work has been done to make the process more flexible and thereby more amenable to automation and computerization. Modern fused coupler operations are highly automated and can make a large variety of products by simply changing a computer file. Similar improvements have also been made in high volume testing so that sophisticated tests of a number of parameters can be performed in a matter of minutes. As the volume and variety of the products have increased over the years, so has the performance. Improvements have been made in reducing excess loss, polarization effects, and wavelength dependence. In addition, higher port count devices (1 X 3, 1 X 4, etc.) have been developed. Numerous studies have been conducted over the years to determine the reliability of these devices. The introduction of glass-to-glass sealing techniques to isolate the fused region by bonding the fibers directly to the quartz substrate significantly improved the stability and long term reliability of these devices. The state-of-the-art production, performance, and reliability of fused coupler technology will be reviewed in this paper.

Environmentally Insensitive Diaphragm Reflectance Pressure Transducer

A novel fiber optic sensor that determines pressure from diaphragm curvature is discussed. This sensing technique exhibits a high degree of sensitivity and linearity and is less susceptible to environmental perturbations than previous intensity modulating techniques. Experimental results are presented for a pressure transducer operational in the 0-60 psi range, and a miniature pressure transducer operational in the 0-5 psi range designed for in vivo medical applications.

Performance Evaluation Of Single-Mode Couplers

In an earlier paper we reported the development of a fusion technique for fabricating environmentally stable, single-mode couplers. During the past year we have fabricated couplers in a production environment and have studied the reliability of the coupler fabrication process. These couplers were designed to have a nominal coupling ratio of 50%. We found that a significant fraction exhibited excess losses of less than 0.05dB. Further, through the use of an automated test facility, we have investigated the performance of the couplers under varying ambient conditions. The test conditions included changes in temperature, variations in the polarization of the input light and variations in the wavelength of the source. In this paper we report the findings of our studies and discuss the implications with regard to the reliability of the fiber optic coupler. This data will allow the designer of a fiber optic system which utilizes single-mode couplers to predict the stability of that system in various environments.

Optimization of tap couplers made by the FBT process

Tap couplers with small coupling ratios (1-10%) play a critical role in monitoring optical fiber systems such as optical amplifiers. They are often used in a feedback control loop and hence must exhibit extreme stability. Very small changes in the operating characteristics of the taps can be interpreted as changes in laser power giving rise to instability in the amplifier gain. Tap couplers made by the fused biconical taper (FBT) process are inherently stable with regard to temperature and, thus, this is usually not a concern. Of much greater significance are the wavelength dependence and polarizastion sensitivity of the tap ratio. Wavelength dependence can be minimized by introducing a mismatch in the propagation constants between the two fibers, but it is also influenced to a lesser extent by the coalescence of the fibers. On the other hand, polarization sensitivity is primarily dependent on coalescence and only somewhat dependent on propagation constant mismatch. As a consequence, it is necessary, in practice, to trade off wavelength dependence against polarization sensitivity in order to optimize the overall stability of the tap coupler. We report here the results of such an optimization study, consistently yielding taps with less than 0.5 dB total change in the insertion loss of the tap leg due to all effects.

Wavelength-Dependent Coupling in Single-Mode Fused Biconical Taper Couplers

Many fiber optic systems in operation today require low loss single-mode couplers to passively split or combine light between two or more single-mode fibers. At present, this need is best met by standard fused biconical taper couplers because of their ease of fabrication and very stable performance over a wide range of operating conditions. However, as single-mode fiber technology transitions from todays predominately long haul applications to tomorrows local area networks (LANs) and subscriber loops, more sophisticated single-mode couplers will be required. For example, many of these systems will likely incorporate wavelength division multiplexing techniques and, as such, will require several types of wavelength dependent couplers. In anticipation of this growing need, three different types of single-mode, wavelength-dependent couplers have been developed at Gould. A discussion of the wavelength dependent coupling in these fused couplers is presented in this paper.

Recent advances in fused fiber optic coupler technology

Refinement and new product development of splitters made by the fused biconical taper process are discussed relative to the emerging technologies of optical fiber amplifiers and practical fiber to the curb telecommunication systems.

Optical performance of recladded couplers

In the fused biconical taper process (FBT) the mode diameter of the optical fields within the fibers are spread to the extent that the surrounding medium acts as the fiber cladding. Usually this medium is air whose optical properties are benign resulting in stable devices. However, if the coupler is recladded with a material other than air, the optical fields spread further into the cladding region and the behavior of the coupler becomes substantially more sensitive to variations in the refractive index of the cladding material. In this paper we report the results of a study of recladded FBT couplers. Experimental results will be presented and compared to the predictions of a model previously used to describe the coupling characteristics of FBT couplers.

1xN broadband fused biconical taper fiber couplers

The fused biconical taper process has been the technology of choice for fabricating a variety of passive fiber optic couplers. These couplers exhibit excellent optical and environmental characteristics. Most recently, this process has been used to fabricate tree and star couplers of various configurations: 1x3, 3x3, 1x4, 4x4 and 1x7 for both local loop and sensing applications. In this paper we report the development of broadband 1x3 and 1x4 couplers for applications requiring simultaneous transmission in both the 1300 and 1550 nm wavelength regions. The wavelength response, insertion loss and optical uniformity of these broadband couplers will be discussed. Their environmental performance will also be presented.