Many assumptions have been made over the years about the correct launch conditions for measuring multimode components. These conditions are usually associated with the type of source used in an optical link, such as an LED or laser. Conventional thinking has been to assume that an LED would angularly and spatially overfill a fiber with light, and by inference, those were the appropriate launch conditions. Similarly, when using a laser source, a more restrictive launch condition has been advocated. Experimental data, investigated during the development of the FDDI standard, has already been reported showing that significant errors can result from these assumptions. The effects of launch conditions on system power budgeting for short optical links with switches, connectors and fiber cables were analyzed. Recent work at Corning has demonstrated that this same situation exists for passive optical fiber couplers. The data below show that errors in link power budgeting can occur when overfilled launch conditions are used to measure optical coupler insertion loss. As was shown previously for other types of passive devices, restricted launch conditions should be utilized with optical couplers to better represent the performance of a device in a real system. Additionally, depending upon the degree of modal restriction in a system, coupler testing shows significant modal sensitivity in parameters such as splitting ratio for optical devices fabricated by some processes and less for other processes. This study examines the behavior of two types of optical coupling devices: fused-biconic taper couplers and ion exchange planar couplers.

In this paper we report the development of a high isolation WDM component for use in a variety of applications incorporating wavelength division multiplexing and demultiplexing techniques. Wavelength isolation in excess of 30dB is demonstrated over bandwidths of 40nm in both the 1300 and 1550nm wavelength regions. The basic operation and performance of the high isolation WDM component will be discussed.

Single mode wavelength division multiplexers (WDM's) are finding wide ranging applications in areas of telecommunications and high performance data links. Many of these applications require isolation performance greater than the standard WDM. The high isolation WDM's presently available however are sometimes a handicap because of their large size. This paper reports details of several compact single mode high isolation WDM's.

Wavelength Division Multiplexers (WDM's) and Wideband Couplers (WBC's) can be fabricated from polarization maintaining fiber. These devices exhibit excellent optical properties and are stable over a wide range of environmental conditions. Possible applications for advanced PM components are discussed.

Photocor (TM) couplers are manufactured using ion-exchange in glass. This paper reports on the extension of this CORNING coupler product line to include high performance multimode stars and ruggedised tree and star couplers for harsh environments. In addition, development work on pigtailed single-mode couplers is presented. Achromatic, polarization insensitive 1 X 2 couplers show 0.8-0.9 dB excess loss at 1310 nm. Insertion loss variations during -40°C/+85°C thermal cycling of packaged devices are less than ± 0.1 dB. The coupler reliability is illustrated with qualification test results.

There is a growing demand for single fiber bidirectional communication systems both in the subscriber loop in the telephony industry and various sensor applications. In such configurations, 1 X2 couplers/ wavelength division multiplexers have become an integral part of such system designs. The single fiber leg of the coupler is normally terminated with a fiber optic connector to provide an interface with the transmission line. In many of these applications there is a requirement for a size reduction in the system and system components. To satisfy this requirement the integration of fused fiber optic couplers or wavelength division multiplexers with fiber optic connectors into a single compact unit has been developed. In addition to the size reduction, elimination of one of the free fiber outputs simplifies system design and reduces the fiber storage requirements.

Both strength and insertion loss of fused couplers are improved by controlling the fusion time and initial thickness of partially etched optical fiber cladding. Coupled power is controlled precisely by the fusion time, prefusion condition before melting, effective coupling length and effective pressure between the fibers. Typical average losses are - 0.48 and 1.45 dB, made of 50/125 μm; - 0.6 and 1.70 dB made of 6/125 μm fibers for 2 x 2 and 4 x 4 couplers, respectively. The strength becomes maximum for a fusion time of 3.0 s. Similar losses and strength are obtained for twin-core optical fiber couplers fused for 3 s. A mathematical model has been developed to analyze the experimental data. Also included is an empirical relation fitting the coupled power vs. core-to-core spacing data of the fiber couplers measured at 850 and 1300 nm.

The technology of surface acoustic wave (SAW) optical frequency shifters is discussed. The construction and operation of such a device with a sideband suppression of 35 dB and a carrier suppression of 29 dB is described. A two pass version of this device gave a conversion efficiency of 10% for 2.5W input electrical power.

In this paper the results of fused biconical-taper (FBT) couplers fabricated with dispersion-shifted fibers are presented. Couplers fabricated by the FBT process possess inherent design advantages of low loss, low cost, and environmental and temperature stability. With the increasing use of dispersion-shifted fiber in long, repeaterless transmission systems, couplers using these fibers are required. The optical and environmental performance of couplers made from four different dispersion-modified fiber profiles is examined.

Intermodulation and harmonic distortions of buried heterostructure distributed feedback lasers can be low enough for many applications, like cable television and microwave subcarrier transmissions. This paper discusses the theoretical analysis and measured values of these distortions. The results indicate that the nonlinearities of lasers are dependent on the modulation frequency, the operating temperature, and the physical structure of the lasers.

A new design of fully FDDI-compliant, fiber optic transceiver in a very compact single-piece integrated package is described. It uniquely implements the full proposed ANSI Fiber Distributed Data Interface (FDDI), Physical Medium Dependent (PMD) function. The transceiver functionality includes a completely FDDI compliant duplex optical connector receptacle together with an electronic circuit which provides the ECL-to-light, light-to-ECL, Transmit_Disable and Signal_Detect services required of the PMD.

We have studied, with computer simulation, optical solitons amplified periodically by stimulated Raman scattering process in single-mode heavy metal fluoride (HMF) fibers for a range of parameters. An optimum single-mode HMF fiber was used to design an all-optical, long distance, soliton based optical fiber communication system. The length-bandwidth product is four times that of a soliton-based optical communication system using present-day single-mode silica fibers. The single channel bandwidth-length product for a bit error rate (BER) less than 10^-9 is nearly 120,000 GHz.km. Typical amplification periods are in the range of 200-300 km; average soliton and pump power are in the range of milliwatts and hence well within the capability of semiconductor lasers.

Comparison of fluoride-based and silica-based fiber on system performance with respect to the repeater link length is analyzed. The effects of dispersion, fiber attenuation, splice loss, source linewidth and fiber unit length on system performance is simulated by computer.

Optical fiber communication is highly successful in the application of undersea and terrestrial trunk links. It is expected to find applications for the subscriber loop networks. Telecommunication in China is undergoing tremendous change due to fiber optic technology and new switching technologies. In this paper we will discuss some of the trends of optical communications in China and make suggestions on its potential developments.

In recent years, much progress has been made in the performance, cost, and standardization of optical fiber connectors and splices. Single-mode fiber connectors and mechanical splices are now routinely available at lower costs than just a few years ago, while at the same time the optical performance of these devices has also improved both in terms of insertion loss and reflectance. Along with these improvements, international and national standards organizations have been drafting the relevant specifications for these devices. Currently there are two important issues related to connectors and splices that are presently being addressed. First, the evolving standards must demonstrate that they indeed guarantee intermateability. Second, the recent reflection requirements that high-bit-rate systems and analog systems have placed of these interconnection devices has resulted in new emphasis on the design and characterization of such devices. This paper will focus on the second of these two current issues, reflectance.

We examine the nature of non-gaussian fields in dispersion-modified single-mode silica fibers. In particular, we show the limitations of using two well-known gaussian approximations for the theoretical prediction of splice loss caused by lateral and angular misalignments. Exact numerical calculations of splice loss with small lateral and angular offsets are compared with approximations obtained by using (i) the Petermann 2 mode-field radius and (ii) the mode-field radius which maximizes the coupling efficiency for gaussian beam excitation. The accuracy of each is discussed.

All experience substantiates that Rotary mechanical splices are completely usable in both digital and analog optical systems. This means that the unique and desirable features of lowest loss, re-enterability and rearrangeability are possible everywhere. Insertion loss and return loss data are presented for four different AM-analog CATV installations that use Rotary splices. In the first of these, Rotary splices, that are polished with 10°-angled ends, are directly compared to fusion. OTDR traces are shown to be the same for both splice types. Furthermore, differences between the two splices for system carrier-to-noise and intermodulation values are indistinguishable.

Experience with the first optical fibre video-communications networks has highlighted the significance of optical fibre jointing techniques which require : a) Reliable joints b) Easily field fitted terminations, bearing in mind the environmental conditions they are used in together with the awkward situations where they may be installed, e.g. telegraph pole, behind facades and in equipment racks. c) Low cost components, due to the high number of connections per fibre kilometre used in these networks. A new product concept has been developed to take account of these various requirements which takes the form of a hybrid, being part permanent mechanical splice and part connector, offering low termination losses associated with splices, together with the capability of being mated and unmated. It offers both low unit cost, with low installation times in the field, compared with conventional connectors. In this new approach, an optical mechanical splice has been developed with plugs on each fibre end to permit connection and disconnection of fibres.

A one-piece molded mechanical splice was developed for easy use in field installations with minimal power loss. The splice is convenient for installing "pigtailed" transmitters, receivers, couplers, splitters and connectors to local area network cable plants. This paper explains the splice design concept and selection of materials for the part, development of a fiber cleaving tool and the index matching material. Dynamic optical test results for the splice using 62/125gm fiber with 900gm buffer are reported for the temperature range -40 to 70°C at 850nm, as well as normal losses at 25°C. Tensile strength measurements for the splice assembly are also given.

A novel size 16 terminus has been developed for use with fiber optic cable in military cylindrical connectors. Based on the use of gradient index lenses, the terminus has been designed for aviation type fiber optic cable. The use of lenses provides expanded beam coupling from one fiber to the second. This allows the termini to to the full range of longitudinal separations to be found in standard military cylindrical connectors without the complex alternative of springs to keep the fiber end faces in near or actual contact. Angular alignment is preserved by close control of tolerances in the pin terminus and the socket terminus alignment sleeve. And excellent resistance to lateral misalignments is one of the principal advantages of expanded beam interconnection. The terminus system avoids any use of epoxies or other adhesives by the use of a novel crimp-and-cleave termination. Besides eliminating the problems of epoxy shelf life, mixing ratio, pot life, mess, and production inefficiency, the new crimp-and-cleave design also requires no electrical power and pro-vides greatly improved termination strength and resistance to bond failure under thermal and tensile loads. Production efficiency is improved because any shortcoming in termination causes the loss of only a crimp sleeve rather than an entire terminus. The termination system has been demonstrated in thermal shock (-55 to +150 C), 1000 hours exposure to 150 C, 24 hour random vibration at 39.6 g's rms, and over 25 other environmental and mechanical tests, with changes in loss consistently under 0.5 dB.

In order to achieve the low-loss splices of single-mode fibers, a new three-dimension high-accuracy automatic alignment system for single -mode fibers has been developed, which includes a new-type three-dimension high-resolution microdisplacement servo stage driven by piezoelectric elements, a new high-accuracy measurement system for the misalignment error of the fiber core-axis, and a special single chip microcomputer processing system. The experimental results show that alignment accuracy of ±0.1 pin with a movable stroke of -±20μm has been obtained. This new system has more advantages than that reported.

Measurements of the LP." even and LP11 odd modes' cutoff in polarization holding filers under periodic deformations reveal the effect of strain dependent cutoff point.

We have studied the design of heavy metal fluoride fibers, having segmented-core refractive index profiles, and operating in a bimodal regime, with small modal dispersion, or good equalization, between the LPN and LP11 modes in 1.3 gm wavelength region. In addition, we have incorporated the concept of effective cut-off, of the LP02 mode, in order to maximize the operating V value. A practical bimodal equalized design example, which has negligible extrinsic losses, is provided in which the equalization between the modes is within ± 25 ps/km over a wavelength interval of 160 nm (- 1.2 μm to 1.36 μm). Hence the predicted bandwidth of the bimodal fiber is high, over a broad wavelength interval.