Eric Y. Chan

VCSEL optical subassembly for avionics fiber optic modules

With the growing maturation of vertical cavity surface emitting laser (VCSEL) technology as a source of commercial off-the-shelf components, the question of VCSEL suitability for use in avionics-qualifiable fiber-optic systems naturally follows. This paper addresses avionics suitability from two perspectives. First, measured performance and burn-in reliability results, determined from characterization of Honeywell VCSELs, are compared with application-based military and commercial avionics environmental requirements. Second, design guidelines for developing a cost-effective VCSEL optical subassembly (VCSEL/OSA) are outlined.

Demonstration of a Gb/S Transceiver with OTDR Built-in-Test for Avionics Local Area Networks

The motivations for development of an integrated BITed transceiver have been described in previous DASC papers (Beranek and Van Deven, 2005). One of the challenges in developing BIT capabilities in avionics local area networks is implementing the BITed transceiver functionality without degrading the transceivers electro-optic performance characteristics, or increasing its size, or changing its multi-source agreement (MSA) standard footprint format. We have successfully demonstrated the first prototype Gb/s fiber optic transceiver with integrated built-in test 10-cm resolution OTDR capability in a small-form-factor (SFF) package. This OTDR BITed transceiver operates at 850 nm with high output power and good electro-optic characteristics over 2 Gb/s. The 10-cm optical time domain reflectometry (OTDR) resolution requires the transceiver to have total rise time (tr ) and fall time (tf) less than 1 ns. This rise and fall time requirement indicates the intrinsic transceiver has to support a 2.5 Gb/s data rate

Potential opportunities for utilizing commercial optoelectronics in avionics fiber-optic networks

Industry studies indicate the feasibility of using both MCM-L/COB and silicon microbench passive alignment technology in harsh, high reliability environments such as military and commercial avionics systems. Moreover, in many cases, if proper design, materials, and packaging approaches, and assembly and quality assurance procedures are utilized, both MCM-L/COB and silicon microbench passive alignment technologies may actually enable design ad manufacturing of low cost avionics optoelectronics modules. Silicon microbench passive alignment packaging technology has been demonstrated for LED, PIN photodiode, VCSEL and edge emitting laser diode packaging. Although MCM-L/COB and silicon microbench passive alignment technologies have been shown to be ruggedizable for the avionics environment, additional reliability testing and infrastructure development work is required before they are implemented in real avionics systems. VCSELs and edge-emitting diode lasers can be reliably used in systems with excursions to high temperature avionics environments) if the total time-at-high temperature is kept modest. Simple temperature measuring circuits and laser diode drive current monitoring circuits for onboard diagnostics and maintenance could be implemented to ensure reliable operations of high-speed laser-based transmitters in the avionics environment.

High performance, low-cost chip-on-board (COB) FDDI transmitter and receiver for avionics applications

Recent trends in the avionics industry have focused on the use of commercial-off-the-shelf electronic components for specialized system applications. Deviating from the conventional concept of high performance at any cost, the idea of producing avionics optoelectronic modules at a low cost-to-performance ratio (or high performance-to-cost ratio) is emerging. Laminate based/Chip-on-Board multichip module interconnect (MCM-L/COB) technology is a robust and flexible packaging approach which has demonstrated its effectiveness in low-cost consumer electronics for many years, and is rapidly finding acceptance in high performance electronics applications. In this paper, we present our results on the development of ARINC 636 compatible Fiber Distributed Data Interface (FDDI) fiber-optic transmitter and receiver modules using MCM-L/COB packaging technology. These modules are equivalent to the industry standard FDDI modules in footprint, but they are required to function with higher performance and be able to operate under more severe environmental conditions than commercial grade components. Through a careful MCM-L design layout and optical subassembly (OSA) selection process, we have demonstrated COB FDDI transmitter and receiver modules that exhibit excellent results over the temperature range of -40 to 110/spl deg/C. Our test results show that the transmitter minimum average output power is about -13 dBm over the operating temperature range. This is 3 dB better than the standard commercial grade FDDI transmitters. Operating at 125 Mb/s, an overall link margin greater than 22 dB can be achieved by these high performance MCM-L/COB optoelectronic modules.

Optoelectronic devices for fiber-optic sensor interface systems

A standardized interface for fiber-optic sensor systems based on wavelength-division- multiplexing (WDM) has been successfully demonstrated using a novel broad-spectrum quantum-well LED and a high-resolution waveguide spectrograph. This efficient interface allows a 40-decibel system loss in 20 sensor channels. The new broadband LED and slab- waveguide spectrograph represent key enabling components for the WDM interface system. The LED produces a spectral width a factor of 3 times larger than that from conventional edge emitting LEDs in the 750-900 nm range. The compact slab-waveguide spectrographs channel resolution (4-5 nm) and grating efficiency (>50%) compare favorably with other multimode WDM elements.

Wireless optical links for avionics applications

Recently there has been strong interest in wireless optical (WO) communication link applications in airplanes and avionics platforms for size, weight, power, cost, and electromagnetic interference (EMI) reduction. Wireless optical link has additional advantage of providing network security because the optical signal from wireless optical link is well confined within an airplane or avionics vehicle. In this paper we discuss some potential wireless optical link applications in commercial airplanes and the challenges in the implementation of wireless optical links for these applications. We will present our experimental results on using white LED (WLED), visible laser source and free-space small-form-factor (SFF) optical transceivers to demonstrate the viability of applying wireless optical links in avionics platforms.

Universal detachable optical connector for military and commercial aerospace fiber optic modules

Packard-Hughes Interconnect has developed a detachable connector for plugging to military and commercial aerospace fiber-optic modules. The connector comprises floating spring loaded fiber-optic termini with 1-mm ceramic ferrules, all contained within a 0.136-in thick, low-profile connector plug body. The connector is mated to the package via a patented retention clip mechanism which secures the plug body to metal posts attached to the package sidewall. Optical alignment between the connector plug terminus and the package is accomplished by an alignment sleeve and mating 1-mm ceramic ferrule mounted in the package nosetube. Connector demating is performed by actuating a release button mechanism integral to the connector plug body. The fiber-optic termini in the connector plug body are easily maintained without replacing the entire connector. This makes the repair/replacement process for a broken fiber pigtail or damaged terminus endface a low cost, fast, and simple operation. The insertion loss for a simplex connector mated to a Boeing FDDI Transmitter receptacle package using 100/140 micrometers graded index optical fiber is less than 0.5 dB at 1.3 micrometers wavelength.

Design of InGaAs strained quantum-well lasers for high-temperature operation

The effect of high temperature on the threshold gain and threshold current density of an InGaAs (GaAs based) strained quantum well laser is examined both theoretically and experimentally. It is shown that designing a quantum well laser for low threshold gain through the use of a long laser cavity and/or high reflectivity facet coatings will reduce the temperature induced threshold current increase. This result is related to the nonlinear dependence of quantum well gain and current density on carrier density. The high temperature characteristics of strained InGaAs and GaAs QWs are also compared.

Optical communications receiver array

One of the major challenges to free space laser communications and ladar is the impact of turbulence on beam propagation, one example of which is signal fading. These impacts can be exacerbated on airborne platforms by turbulence in the vicinity of the laser system aperture and the platform wake. There are a number of strategies to mitigate this, including adaptive optics, active flow control, and various dimensions of diversity: wavelength, polarization, temporal, and spatial diversity. In this paper we will discuss spatial diversity implemented in the focal region of optical telescopes. We will briefly compare this with other methods, describe results of requirements analysis of array features and optical configurations for various atmospheric turbulence states, and suggest several attractive configurations. We will also report on the design and test of one configuration, implemented in a prototype, and tested for noise performance, optical transmission, modulation bandwidth, and BER performance with our dynamic turbulence simulator. Early evidence shows significant BER improvements of several orders of magnitude at high turbulence fluctuation frequencies using this technique.

Hermetic fiber optic modules for avionics applications

In the past, Boeing had successfully developed and produced the hermetic ARINC 636 fiber optic transmitter and receiver modules for the PLANET System in the Boeing 777 commercial airplanes. These hermetic fiber optic modules had demonstrated over 4 millions aggregate flight hours with zero failure; the hermetic fiber seal technology is a key contributor to this outstanding reliability record. Recently, we have investigated failure mechanisms in commercial-off-the-shelf (COTS) hermetic mini-dil (dual-in-line) laser diode modules; and developed new hermetic fiber seal process for low cost mini-dil form factor packages. In addition, we are also developing cost effective hermetic multi-channel fiber optic array modules technology for aerospace applications.