Gair D. Brown

Bandwidth and rise time calculations for digital multimode fiber-optic data links

The use of multimode fiber in digital fiber-optic data links requires simple and accurate procedures for the calculation of data line component bandwidth and rise time responses. The author investigates source/fiber/detector interactions, to develop a simple model for multimode fiber system information capacity. Simplified expressions for the baseband impulse and frequency responses of each component are given along with relationships between the theoretical impulse response root mean square (RMS) width and the component rise time or bandwidth. The application of the central limit theorem to the system yields expressions for the composite system rise time and bandwidth which contain correction factors to those that would be obtained using the normal Gaussian assumptions. >

Chromatic dispersion measurement in graded-index multimode optical fibers

The chromatic dispersion observed in a graded-index multimode optical fiber is a function of the radial position of the launched light. When a graded-index multimode optical fiber is overfilled spatially and angularly, the chromatic dispersion observed is an average (composite) chromatic dispersion over all of the possible launches. Under certain assumptions, the relationship between the chromatic dispersion observed for the overfilled fiber and the chromatic dispersion of any restrictive launch can be determined. This relationship can be used to predict the composite graded-index multimode optical fiber chromatic dispersion from the measurement of the chromatic dispersion of a single simplified launch, such as a single-mode fiber launch. Preliminary experimental results confirm this approach. >

The Development Of Steady State Modal Conditions In Short Length Concatenated Systems

The development of steady state modal conditions in several short length concatenations was studied. The resultant steady state distribution was identified as approximately equivalent to a 70/100 beam optics launch into a short reference fiber. Mechanical methods of reproducing the distribution in a short length of fiber with an initial overfill condition were also studied.

System design methodology for power budgeting of 62.5 mu m multimode fiber systems

The authors present the data to support a recommendation of a new system loss budgeting rule applicable to high-component-count systems using 62.5 mu m core diameter multimode fiber. The limited phase space or restricted launch characterization of fiber is demonstrated again to give the most accurate system loss prediction. However, for this fiber size, components such as connectors, switches, and couplers are shown to exhibit loss equivalent to the overfilled launch loss. Two mechanisms are found to explain why the overfilled launch component loss best characterizes their actual loss in common multimode fiber systems. Both are related to the large numerical aperture (NA) of the power distribution launched by the light-emitting diode (LED) system sources. It is important to note that these mechanisms only have been observed on components made with 62.5 mu m multimode fiber. This behavior is likely to be different in other fiber sizes. >

Long-term performance of fiber optic cable plant in Navy ships

A fiber optic cable plant installed on the AEGIS cruiser USS Mobile Bay (CG 53) provides the opportunity to study the long term effects of the shipboard environment on passive fiber optic components. The current study consists of periodic inspections of the cable plant, including visual examination of connectors and OTDR measurements of the fibers. Measurements to date show no significant adverse impact to the performance characteristics of the fiber optic components from the shipboard environment.

High-impact shock testing of fiber optic components

MIL-S-901 High Impact Shock tests were performed on commercial-grade and ruggedized fiber optic connectors, splices, and switches. Both singlemode and multimode connectors and splices were tested. Only multimode switches were tested. Transient losses of varying magnitudes and durations were observed. Most components suffered no permanent degradation.

High impact shock testing of fiber-optic components

Abstract MIL-S-901 High Impact Shock tests were performed on commercial-grade and ruggedized fiber-optic connectors, splices, and switches. Both single-mode and multimode connectors and splices were tested. Only multimode switches were tested. Transient losses of varying magnitudes and durations were observed. Most components suffered no permanent degradation.

Vibration Testing Of Fiber Optic Components

Vibration tests were performed on commercial grade fiber optic connectors and splices. Both singlemode and multimode components were tested. Sinusoidal vibrations up to 500 Hz and random vibrations up to 2000 Hz were applied. Analog modulation was negligible and no permanent damage was observed.

Assigning Loss Budgets To Fiber Optic Components In Adverse Environments

Using fixed power margins in fiber optic system power budget calculations does not adequately account for the nature and complexity of a fiber optic link. In an adverse environment scenerio the power margin must be sufficient to guarantee link operation throughout all expected conditions. A variable margin dependent upon the nature and number of the components in the link provides a more acurate estimate of the margin required for a link than a fixed margin. One particular method of estimating each components portion of the environmental margin is presented.

Temperature And Humidity Testing Of Fiber Optic Components

Temperature and humidity tests were performed on commercial grade fiber optic couplers, connectors, splices and optical,fiber. Both singlemode and multimode components were tested. Temperatures ranged from -54°C to +65°C or +85°C depending on the component application. In the humidity tests the relative humidity was maintained at greater than 95 percent above 20°C. Changes in optical transmittance of varying degrees and permanent damage were observed and recorded.