Search

A pediatric prenatal visit during the third trimester is recommended for all expectant families as an important first step in establishing a child's medical home, as recommended by

Keloids negatively impact the health and quality of life of many affected dermatologic patients. Treating keloids is often difficult, and suboptimal responses are frequent. Fortunately, there are many treatment options available to the clinician that may lead to improved clinical outcomes. We present a review of currently available therapeutic options. Intralesional steroid injection remains the first-line treatment for keloids. Imiquimod, direct interferon therapy, or intralesional 5-flurouracil may alleviate the need for excessive corticosteroid therapy. Radiation and laser therapy are emerging therapeutic options that have demonstrated efficacy in reviewed studies. Given the unsatisfactory outcomes associated with pressure dressings, vitamin E, ablative laser, and surgical excision, these options should be avoided in keloid management. Further research is needed to evaluate the efficacy and recurrence associated with the reviewed therapeutics.

Background Vitiligo is an acquired multifocal and polygenic dyschromia that affects 1% to 3% of the world and presents as multiple depigmented macules and patches. Traditionally, the treatment of vitiligo has focused on pharmacologic interventions, but nearly half of all treated patients fail to respond successfully. Objective Several advanced techniques exist that can aid dermatologists in treating vitiligo in patients who do not respond favorably to traditional pharmacologic treatments. These advanced interventions include the use of the 308-nm excimer laser, total body depigmentation therapy with monobenzyl ether of hydroquinone, microdermabrasion, micropigmentation, khellin-UVA therapy, and surgical management using miniature punch grafting, suction blister grafting, and epidermal cultures. Materials and Methods This article reviews the current literature on these advanced treatment modalities for vitiligo and provides a practical guide for application of these techniques. Results and Conclusion Our ability to treat vitiligo may be imperfect, but through appropriate patient selection and careful application of one or more of these advanced therapies, successful treatment of vitiligo, even in patients refractory to treatment, can be achieved.

Background Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma, which typically presents as a patch or plaque in early-stage disease. Phototherapy including psoralen plus ultraviolet A and ultraviolet B are well-established treatment modalities in management of early-stage MF. Only a limited number of reports have evaluated the efficacy of 308-nm excimer laser in therapy of cutaneous T-cell lymphoma. Objective We sought to evaluate the efficacy of 308-nm excimer laser (XTRAC, PhotoMedex, Montgomeryville, PA) in patients with stage IA to IIA MF. Methods We reviewed the clinical and laboratory characteristics of 6 consecutive patients given the diagnosis of refractory MF who underwent treatment with excimer laser. Results We found that the 308-nm excimer laser is a safe and well-tolerated alternative therapy for early-stage MF. In addition, we were able to delineate criteria to help predict treatment response. Our data showed that 4 (66%) patients achieved clinical improvement (3 complete responses, 1 partial response), 1 had stable disease, and 1 had progressive disease. Limitations This was a retrospective study consisting of 6 patients. A prospective study with a larger sample size would be desirable for future studies. Conclusion The use of 308-nm excimer laser in the treatment of stage IA to IIA MF showed clinical and pathological benefit for patients with isolated lesions or lesions in areas that may be difficult to treat because of anatomic location.

Facial lipoatrophy can be socially disfiguring, often prompting patients to seek correction. A variety of agents are used to treat facial lipoatrophy, but the quest for the ideal agent remains elusive. We present a case of non-HIV associated, idiopathic hemi-facial lipoatrophy successfully treated with autologous fat transfer (ATF). Because ATF has no complications from antigenicity, it is a safe and cost-effective treatment option for patients with non-HIV associated cases of facial lipoatrophy and abundant donor tissue.

Most patients with localized nodules should receive topical treatment first. But disappointing results or specific findings described here could necessitate additional or alternative options.

Topical chemotherapy, topical immunomodulators, or intralesional chemotherapy may be used to treat nonmelanoma skin cancer (NMSC).To review the cost and efficacy of topical and intralesional therapies for NMSC.Literature search assessing the efficacy of NMSC treatment with topical imiquimod, topical 5-fluorouracil (5FU) intralesional 5FU, methotrexate, bleomycin, and interferon (IFN). Single-lesion case reports were excluded. Aggregate cure rates and the estimated cost of treatment (including excision and repair of recurrent lesions) for a sample 1-cm lesion on an extremity were calculated.Cure rates ranged from 65% to 100% for topical imiquimod and 61% to 92% for 5FU. For intralesional agents, cure rates varied considerably according to medication used and NMSC subtype treated. Keratoacanthomas had high cure rates with intralesional agents: 98% for 5FU, 91% for methotrexate, 100% for bleomycin, 100% for IFN alpha (α)-2, 83% for IFN α-2a, and 100% for IFN α-2b. Estimated costs (excluding medication cost) ranged from $205 (intralesional methotrexate for keratoacanthoma) to $1,174 (IFN α-2a for superficial basal cell carcinoma).Nonsurgical management of NMSC remains a viable and relatively cost effective treatment option in select cases. Providers should consider the relative efficacy and cost of each medication when using nonsurgical modalities.

Vitiligo is a depigmenting disorder characterized by the progressive loss of melanocytes. In cases of extensive vitiligo that is unresponsive to treatment and involves noticeable areas, such as the face and hands, total depigmentation is a clinical option. The choice to depigment is a difficult one for the patient given the irreversible nature of treatment and the psychosocial implications of skin color change. This issue can be particularly complex for black patients. Depigmentation has been practiced for decades and documented in the literature, but the practice in Fitzpatrick skin type VI is not well-documented. We present a case of depigmentation in a patient with Fitzpatrick skin type VI, as well as technical options for depigmentation, the clinical approach, patient preparation, and psychosocial issues involved with this treatment option.

Add-drop filters are demonstrated using silica-on-silicon optical waveguide technology. This device consists of a full directional coupler subdivided by Mach-Zehnder sections. Tapering of the coupling coefficients is experimentally shown to dramatically reduce the filters' sidelobes. Only one photolithographic step is required using the silica planar waveguide technology, yielding accurate wavelength control of the filters. Excellent agreement between measurement and design was achieved. >

Objective: Vitiligo is a common depigmenting condition that carries a high psychosocial morbidity. Many of the current topical and light therapies aid in repigmentation but require extensive treatment periods and carry unwanted side effects. The excimer laser is a newer treatment option that can induce repigmentation in an abbreviated time frame without global exposure to radiation. This case series provides further evidence to support the use of excimer laser in treating vitiligo especially of the face. Design: Patients with extensive facial depigmentation were treated with excimer laser twice weekly and calcipotriene daily until they developed significant repigmentation. Setting: Evaluation and treatment was performed at the Veterans Affairs outpatient dermatology clinic in Tampa, Florida. Participants: Three patients with Fitzpatrick skin types IV to VI were selected. These patients had failed a variety of topical treatments including steroids and calcipotriene, but were light naïve prior to beginning the study. Measurements: The primary outcome measure employed was percent repigmentation by visual estimation. The average dose of radiation, number of treatments, and weeks of therapy were also recorded. Results: All three patients experienced greater than 75 percent repigmentation of their facial vitiligo over a treatment course from 10 to 20 weeks. Conclusion: The excimer laser is a viable treatment for vitiligo and may yield results more expeditiously than other commonly utilized therapies. The rapid response may be correlated with skin type, but a more extensive study needs to be undertaken to further evaluate this correlation.

The Centers for Disease Control (CDC) have recently lowered the acceptable blood lead concentration in young children fromor = 25 toor = 10 micrograms/dl (or = 1.21 toor = 0.48 mumol/L). The incidence of lead toxicity with respect to geographical areas and socioeconomic status has not yet been defined. We evaluated the incidence of increased lead concentration in inner-city, suburban, and rural children aged 9 months to 3 years. Seven hundred eighty of the 4,196 studied inner-city samples (18.6%) had lead concentrationsor = 10 micrograms/dl (0.48 mumol/L), of which only 71 (1.6%) had lead valuesor = 25 micrograms/dl (1.21 mumol/L). Only 5 of the 212 studied children (2.4%) from suburbia and 7 of the 120 children (5.8%) from rural communities had blood lead concentrationsor = 10 micrograms/dl (0.48 mumol/L). None of these children, however, had a lead concentrationor = 15 micrograms/dl (0.73 mumol/L). In contrast, 276 inner-city subjects (6.6%) had lead valuesor = 15 micrograms/dl (0.73 mumol/L). Our data indicate that a correlation exists between geographical location and blood lead concentration in young children. Government health agencies at all levels should prioritize their limited resources for those areas that are most at risk for lead poisoning.

Keloids and hypertrophic scars are abnormal responses to wound healing. In general, keloids may exhibit proliferative growth beyond the margins of the scar and will remain persistent; whereas hypertrophic scars will stay contained to the original wound and may regress over time. The authors will discuss the five different types of keloid: post-incisional, ear lobe, spontaneous, acne keloidalis nuchae (AKN) and sessile. Many medical and surgical modalities have been studied in the treatment of these two entities, ranging from silicone sheets, intralesional corticosteroid injections, cryosurgery, ligation, 5- fluorouracil, Allium cepa (onion) extract, lasers, imiquimod, interferon-a and intralesional verapamil and surgical excision. This review will discuss the pathogenesis, types and treatments for keloids and hypertrophic scars.

Similarities between fiber bandwidth spectra and loss spectra are found to occur. Wavelength-dependent far-field radiation patterns were used to deduce that high OH ion concentrations, near the center of the core, caused differential attenuation of low-order modes. This resulted in bandwidth peaks at the same wavelengths where water absorption loss peaked.

Dispersive differences between B(2)O(3) and SiCO(2) constituents make nonparabolic profiles optimal equalizers of intermodal group delays in fibers with graded B(2)O(3)-SiO(2) cores and uniform B(2)O(3)-SiO(2) cladding. Pulse dispersion measurements were correlated with profile shapes in a systematic study of multimode fibers with near power law gradients. Far field spatial ray filters were used to diagnose impulse response shapes so that new fibers could be fabricated with closer-to-optimal profile gradients. One of the fibers had an alpha approximately 1.77 power law exponent that was nearly optimal for lambda = 907.5-nm wavelength and caused 2sigma = 0.26-nsec/km full rms output pulse spreading. When expected material dispersion effects were deconvolved from the output pulse spreading, the resultant pulse width was approximately 75 times less than the result expected for a comparable step-index fiber. This is the largest pulse width reduction reported yet.

The loss spectra, refractive-index profiles, numerical apertures, and pulse dispersion characteristics of three multimode optical fibers made by Corning Glass Works have been measured at Bell Laboratories. The lowest transmission loss, 4.3-6.8 dB/km, was observed at 1.06-microm wavelength; in the 0.8-0.9-microm spectral region the losses ranged from 6.6 dB/km to 11.6 dB/km. The numerical apertures of the fibers, designated as Nos. 1, 2, and 3, were calculated from the measured refractive-index differences to be 0.133, 0.157, and 0.121, respectively. Pulse dispersion due to multimode effects in fiber No. 1 (1 km long) was 8.4 nsec at 0.9-microm wavelength; the values were 6.0 nsec for fiber No. 2 (0.363 km long) and 2.6 nsec for fiber No. 3 (0.290Km).

Microscopic lenses, fabricated on optical fiber surfaces, have quadrupled the efficiency for coupling astigmatic beams from GaAs junction lasers into 4-microm cores of single-mode fibers. A novel photolithographic technique was used to make hemispherical and hemicylindrical microlenses, with diameters between 4 microm and 10 microm, from commercially available negative type photoresist that is transparent at ir laser wavelengths. Geometrical profiles of photoresist lenses, documented with scanning electron photomicrographs, were remarkably smooth even though their dimensions were more than an order of magnitude smaller than other known lenses.

The feasibility of using a variety of rare-earth doped optical fibers for measuring spatially averaged temperatures from approximately 0 to approximately 100 degrees C over distances of 10 to 20 m is discussed. Such distributed temperature sensors would be particularly well-suited for building climate control systems and industrial processing applications. The temperature-dependent absorption spectra of 6 MCVD processed fibers containing different concentrations of Nd/sup 3+/, Pr/sup 3+/, and Yb/sup 3+/ rare-earth ions were characterized and used to determine thermally active dopant species, optimal dopant concentrations, and most sensitive operating wavelengths for use as dual wavelength distributed temperature sensors. >

We present a theoretical analysis of highly elliptical optical fibers by expanding the vector fields as a series of orthogonal functions. Higher-order cutoff values of the normalized frequencies (V numbers) are evaluated for step-index fibers of varying ellipticities. The effect of different refractive-index profiles on the birefringence of the fiber is presented. For fibers operated in the two-mode regime, we discuss the effect of ellipticity and refractive-index profile on the differential propagation constant (Deltab) related to the scalar equivalent of LP(0l) and LP(11)(even)modes.

Transmission of 50-psec solitons in a 75-km recirculating loop of dispersion-shifted fiber (D = 1.38 psec/nm/km at lambda(s)), using low-gain erbium amplifiers spaced 25 km apart, displays jitter in pulse arrival times consistent with low error rates for transmission over 9000 km and for bit rates ?4 Gbits/sec. Furthermore, a study of soliton pair propagation in the same loop shows no significant interaction over 9000 km for pair spacings/=5tau.

A numerical parametric study is used to gain insight into how the shapes of dispersion and bandwidth spectra are influenced by dimensions and index differences of light-guide structures with two claddings. Computer-simulated fibers are demonstrated to have bandwidths greater than 25 GHz-km across the entire 1.3-1.55-microm wavelength region.

A low-loss triangular-profile single-mode fiber is reported. The fiber loss at 1.3-1.55microm wavelengths is below 0.4 dB/km, and its zero-chromatic-dispersion wavelength is 1.402 microm.

The advent of highly active anti-retroviral therapy (HAART) has extended the lives of patients affected by human immunodeficiency virus (HIV) disease. A common cutaneous side effect of HAART is facial lipoatrophy. The hollowed out cheeks, temples and eye sockets often lead to a gaunt cachetic facies which can be a disconcerting stigmata of the disease and a psychological burden to the patient. Autologous fat transfer (ATF) is a minimally invasive surgical procedure that can temporarily improve the appearance in patients with facial lipoatrophy. Other corrective procedures (e.g., injectable fillers) are available, but, to date, the ideal procedure for permanent correction of facial lipoatrophy has not been found.

The fiber for the sensor is formed by cladding fused silica during drawing with polydimethyl siloxane into which an organic fluorescent dye, 9, 10-diphenylanthracene, has been dissolved. Upon side illumination at a wavelength within the excitation range of the dye, the cladding fluoresces; some of this fluorescence is coupled into guided modes in the fiber core through the evanescent fields of these modes. In the presence of oxygen, fluorescent emission by the dye is diminished. For the sensor described, the rubbery liquidlike nature of the polydimethyl siloxane cladding allows rapid diffusion of gases, and the intensity of the guided fluorescence is observed to drop by 30% in less than 5 s when the ambient atmosphere changes from pure nitrogen to pure oxygen. The advantages of this sensing technique, and some of the possibilities for new sensors based on this principle, are discussed. >

An attempt to relate polarization dispersion directly to some physical property and then use this as a means by which to characterize polarization-mode dispersion (PMD) is reported. A new diagnostic procedure has been developed and tested for screening dispersion-shifted (DS) fibers with PMD due to core ellipticity. Measurements of far-field radiation profiles across major and minor core axes are used to characterize polarization-mode dispersion. This technique is a relatively simple and quick method of screening dispersion-shifted fibers for polarization-mode dispersion greater than 5 ps/km. Differences in these far-field pattern widths were then correlated with direct core ovality measurements performed using the near-field refraction technique. The authors outline the test procedure in detail, analyze sources of error, and discuss detection limitations. >

A fiber optic chlorine sensor having its entire length as the sensing element is reported here. The fiber consists of a silica core and a chlorine-sensitive cladding. Upon exposure to chlorine, the cladding very rapidly changes color resulting in attenuation of the light throughput of the fiber. A two-meter portion of sensor fiber responds to 10-ppm chlorine in milliseconds and to 1 ppm in several seconds. Furthermore, response to 100 ppb chlorine is realized in minutes. The high sensitivity suggests that the propagating modes of the light interact strongly with the cladding, and that these interactions are massively increased (Beers Law) due to the extended sensor length. The sensitivity to 1 ppm chlorine gas as a function of the length of fiber exposed between 0.3-30 meters is presented. The sensitivity to concentrations of chlorine from 0.1ppm-10ppm has been determined for a fixed 2 meter length of fiber. Pre-exposure fiber attenuation measures 70 dB/km (@ 633 nm) making it possible to detect chlorine on a continuous length of fiber on the scale of one hundred meters or more using standard detection methods (e.g. laser and photodetectors). This will replace the need of having a collection of point-detectors to cover large areas.

Endoscopic sphincterotomy has been used for the treatment of many biliary disorders, including extraction of obstructing common bile duct stones. Manometric studies of the sphincter of Oddi and the common bile duct have shown a marked decrease in biliary tract pressures after sphincterotomy. A prospective study of 12 patients with intact gallbladders using hepatobiliary imaging before and after sphincterotomy was performed to assess changes in bile dynamics. Nonfilling of the gallbladder occurred in 9 of the 12 patients after sphincterotomy, indicating significant alteration of bile flow. Such changes in bile dynamics may have serious implications in patients selected for medical dissolution of gallstones. It may also adversely affect specificity of cholescintigraphy in diagnosing acute cholecystitis.

The Letter shows that a commercial optical time domain reflectometer can be modified to measure the statistical nature of polarisation mode dispersion along the length of a communications grade fibre with short-length PMDs > 4 ps/km.

The “resonant coupler” (RC) add-drop filter is a 2x2 device that diverts one of N input wavelengths into one output while the remaining N-l wavelengths couple into the second output. Specifically at off-resonance wavelengths, light is transmitted in the “bar state” from the input to the corresponding output. However at the resonant wavelength coupling occurs, and light is transmitted from the input to the “cross state” located at the opposite output: hence the name resonant coupler. The RC functions like Bomholdt et. al.’s ‘meander coupler’ll], however our device requires only one mask level and has more accurate control of the resonant wavelength. An example of a RC is shown in Fig. 1. expanded 50x in the vertical. The RC consists of a series of parallel waveguide couplers connected by waveguides of unequal arm lengths. In the case of only two couplers, the device reduces to a MZI. Resonance is achieved by making the path length difference the same for all pairs of arms. Furthermore, the coupling strengths can be tapered to substantially suppress the passband sidelobes. To separate the waveguide coupling from the path length difference we have introduced identical curved paths in both waveguides in to and out of the couplers such that the path length difference, while the waveguides are coupled, is negligible.

Abstract 4990 Background: Mycosis fungoides is the most common type of cutaneous T-cell lymphoma. Early stage disease is effectively managed with skin directed therapies such as UV light and topical steroids. Excimer laser (EL) delivers monochromatic, UVB light at a wavelength of 308 nm via hand held device that covers an area of 2 × 2 cm. It generates a short-pulse radiation that is concentrated on an affected area of skin, thereby allowing a delivery of higher dose on precisely targeted tissue. In contrast to other phototherapy techniques such as narrow band UV light, the EL is ideally suited for patients with small number of patch lesions. Although EL was successfully utilized in the management of psoriasis and vitiligo, there is not extensive experience with this modality in patients with CTCL. Objectives: To assess safety and efficacy of EL therapy in patients with early stage MF who failed ≥1 skin directed therapy. Design and Methods: This is a retrospective analysis of seven consecutive patients with stage 1 MF treated with EL phototherapy between January 2011 and August 2011 in a single institution. Seven patients with histologically confirmed common type MF, and one patient with folliculotropic MF received 308 nm EL therapy after failure of at least one prior skin directed therapy. The median age was 48 years (range 24–77 yrs). Four (57%) were male, 3 (43%) were female, six (86%) were Caucasian, and 1(14%) were African American. Biopsies and photos were obtained at diagnosis and after the completion of 24 treatments. Results: Treatment was initiated at a dose of 200 millijoules (mJ) and was increased by 10–15% each subsequent treatment. The max dose of treatment ranged from 240 mJ to 850 mJ. The total number of administered treatments was 24 delivered over period of 3 months. The median number of treated lesions was 2 (range 1–5). The surface area of treated lesions was Conclusion: Our results suggest that EL is effective and well tolerated skin-directed treatment modality for selected patients with early stage MF. However, longer follow-up will be required to assess durability of responses. Advantages of this approach include shorter treatment duration and lower risk of carcinogenesis in the non-affected areas of skin. Prospective study with a larger cohort of patients is necessary to further assess efficacy and safety of this approach. Disclosures: No relevant conflicts of interest to declare.

Polarization mode dispersion (PMD) in dispersion-shifted fibers presents an inherent limitation in ultralong-distance communications systems. The advent of multigigabit-per-second systems and CATV applications makes it imperative that a good measure of PMD be obtained during fiber manufacture. Several techniques for the measurement of short-length PMD in fibers are currently available.1 A typical spool of fiber, however, has PMD values that vary along the length owing to minor perturbations during fabrication. As a result, a short-length PMD measurement on a specific section of a fiber made by using any of the techniques does not provide a complete knowledge of the statistical spread of PMD over the entire length. In this paper we show that by modifying a commercial optical time-domain re- flectometer (OTDR) with a polarizer/analyzer pair, one can measure short-length PMD’s in fibers.

Using an optical fiber whose transmission loss depends in a linear way on temperature, a thermometric system can be designed that will allow direct measurement of the temperature averaged along the length of the fiber. This paper describes such a system used to test the feasibility of using rare earth-doped fibers in practical distributed measurements of average temperature.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using an exact waveguide analysis and measured stress profiles, we show that a delicate interplay between form-induced and stress-induced contributions to polarization mode dispersion in dispersion-shifted fibers can significantly reduce intrinsic short-length polarization mode dispersions. Our observations also indicate that the ovality of fibers is not a true indicator of long-length polarization mode dispersion in production-quality cabled fibers.

Sir.—The Centers for Disease Control, Atlanta, Ga, have recently lowered the acceptable blood lead concentration in young children from 1.20 μmol/Lor less to 0.50 μmol/L or less.1Lead values of 0.50 to 1.20 μmol/L have been shown to be associated with decreased intelligence and impaired neurobehavioral development.2,3Specific social and medical interventions are now deemed necessary in this lead concentration range for exposed children.1 Although the incidence of toxic levels of lead in young children, using the new criteria, is not well established, it is expected to have a significant impact on the medical community. In addition, federal, state, and local health care resources will be adversely affected. In this report, we describe the incidence of lead poisoning in 2837 young inner-city children from the General Pediatric Ambulatory Clinic at Children's Hospital in Washington, DC. Materials and Methods.—Intravenous blood specimens were randomly studied for lead

We study propagation characteristics of double-mode fibers by measuring group delay differences of time-resolved discrete pulses of the LP(01) and LP(11) modes as a function of wavelength in the 1.06- to 1.6-μm region. The technique has been used to make the first measurements of zero intermodal dispersion in the zero material dispersion region of graded-index double-mode fiberguides that can have larger diameters than standard single-mode fibers. The results can also be used to deduce information about the fiber's refractive-index profile, such as δ, the normalized peak refractive index difference.

We describe the performance of an experimental 1.5-μm lightwave transmission system operating at 8 Gbit/s over 68.3 km of single-mode fiber. The dispersion penalty is limited to 1 dB through the use of external modulation and is attributable to the intrinsic information bandwidth.

A newly developed technique for directly measuring fiber dispersion in the frequency domain as a function of wavelength is described. Spectrally filtered white light from a xenon arc lamp is sinusoidally modulated in the range 0 to 1 GHz by an electrooptic modulator and injected into a fiber. The procedure is to vary the modulation frequency and measure the corresponding sideband output power with a photomultiplier and spectrum analyzer. Ratio measurements between the test fiber and a short reference fiber give the baseband frequency response. A number of germanium- and boron-doped fibers have been examined. The least dispersive borosilicate graded-index fiber has a 1 dB bandwidth of 1 GHz, after 1.07 km of propagation at λ = 908 nm. The width broadens gradually with increasing wavelengths up to λ = 1100 nm.

Silica tubing to be used as substrate tubes for MCVD has was demonstrated for a fiber having only one-fourth the deposited clad-merical tubing in that it is both dehydrated and fluorinated during processing to yield a silica which is dry and whose refractive index is lower than that of silica. These tubes are advantageously used to prepare single-mode fibers having fluorinated-silica cladding which controls dispersion and reduces scattering losses. In this case, the refractive index of the deposited cladding can be matched to that of the outer tube thus avoiding leaky-mode losses commonly encountered in depressed-index clad fibers. Using such an approach, low loss (0.28 dB/km at 1.55 μm) was demonstrated for a fiber having only one-fourth the deposited cladding required when a commercial silica tube is used. Such tubes could provide ecomomies to the processing of and the performance of complex cladding single-mode structures and impact multimode fiber designs.

Loss and bandwidth spectra were measured in the longest length of single-mode MCVD fiber drawn to date. The 21.7-km-long fiber guide has a 0.5 percent index difference between its 7-μm-diameter core and cladding. Chromatic dispersion effects resulted in a minimum dispersion at a wavelength near 1.35 μm. At 1.30 μm, the fiber loss and bandwidth were measured at 1 dB/km and 21 GHz km (source linewidth = 4 nm), respectively. Potential system performance was estimated from calculations of dispersion power penalties and chromatic-dispersion-limited repeater spacings for 274- and 548-Mb/s data transmission rates. A new numerical parametric study was used to show how the bandwidth of a fiber can be optimized by properly choosing its core diameter and core-to-cladding index difference.

Intermodal dispersion properties are compared for high silica fibers with borosilicate (B 2 O 3 -SiO 2 ) and germania borosilicate (GeO 2 -B 2 O 3 -SiO 2 ) graded-index profiles. Pulse transmission measurements were systematically correlated with profile shapes so that new fibers could be fabricated with closer-to-optimal profile gradients at a wavelength of 907.5 nanometers. Germania borosilicate fibers with power law profile exponents (α ≈ 2.03) lowered intermodal dispersion 50 times from the result expected for comparable step-index fibers with N.A. ≈ 0.19. By contrast, borosilicate fibers with α ≈ 1.78 caused a 100-fold pulse width reduction in fibers with N.A. ≈ 0.14, corresponding to a 2σ = 0.13 ns/km pulse-broadening rate.

This paper describes state-of-the-art measurement techniques for the characterization of fiber loss and dispersion. Special emphasis is placed on the achievement of high measurement accuracy, and on novel techniques to determine the loss and dispersion of single-mode and graded-index fibers in the 0.8 to 1.7-µm wavelength region where fiber loss and material dispersion are both small.

Using a multiplexer and demultiplexer built from discrete GaAs FET's, a directly modulated distributed feedback laser, and a low capacitance avalanche photodiode receiver, we have achieved transmission at 4 Gbit/s over 103 km of single-mode optical fiber at 1.54 μm.

Heavy metal halide glass fibers have the potential of optical loss between 0.001 and 0.01 dB/km in the 2-10 \mu m region. We have evaluated some of the system aspects of these fibers in order to determine the ultimate performance limits and to assist in defining waveguide design and fiber processing techniques. Extrinsic waveguide-related losses and limitations including microdeformation, optical nonlinearities, dispersion characteristics, and source and detector capabilities become more significant as the intrinsic losses decrease. Two representative halide glass systems are discussed: a heavy metal fluoride operating at \simeq 2 \mu m and a heavy metal chloride glass at \simeq 6 \mu m. The results indicate that repeater spacings ≳ 1200 and 3600 km at \lsim 1 Gbit/s may be possible for chlorides and fluorides, respectively.