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Publications (3)0 Total impact

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    ABSTRACT: We have developed plugless optical transceivers for low cost optical networking with plastic optical fiber (POF). The transmission speed is 125 Mb/s for Ethernet applications and 1.25 Gb/s for Gigabit Ethernet and other high speed applications. The high speed modules for Gigabit transmission are based on a red VCSEL light source for the transmitter that matches the optical attenuation minimum of the plastic fiber media. The devices have demonstrated excellent reliability with more than 850,000 hours of mean-time-to-failure operating life time at elevated temperatures of 40degC. Automotive qualified, rugged resonant cavity LEDs (RCLEDs) are used for the lower speed modules. The plugless transceiver design enables the direct optical connection between the active components and standard POF without the need for special termination of the fiber. Only a simple cutting action is required. This enables low cost field installations.
    Electronics System-Integration Technology Conference, 2008. ESTC 2008. 2nd; 10/2008
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    ABSTRACT: There are many potential applications of visible, red (650nm – 690nm) vertical cavity surface emitting lasers (VCSELs) including high speed (Gb) communications using plastic optical fiber (POF), laser mouse sensors, metrology, position sensing. Uncertainty regarding the reliability of red VCSELs has long been perceived as the most significant roadblock to their commercialization. In this paper we will present data on red VCSELs optimized for performance and reliability that will allow exploitation of this class of VCSEL in a wide range of high volume consumer, communication and medical applications. VCSELs operating at ~665nm have been fabricated on 4" GaAs substrates using MOCVD as the growth process and using standard VCSEL processing technology. The active region is AlGaInP-based and the DBR mirrors are made from AlGaAs. Threshold currents are typically less than 2mA, the devices operate up to >60C and the light output is polarized in a stable, linear characteristic over all normal operating conditions. The 3dB modulation bandwidth of the devices is in excess of 3GHz and we have demonstrated the operation of a transceiver module operating at 1.25Gb/s over both SI-POF and GI-POF. Ageing experiments carried out using a matrix of current and temperature stress conditions allows us to estimate that the time to failure of 1% of devices (TT1%F) is over 200,000h for reasonable use conditions – making these red VCSELs ready for commercial exploitation in a variety of consumer-type applications. Experiments using appropriate pulsed driving conditions have resulted in operation of 665nm VCSELs at a temperature of 85 o C whilst still offering powers useable for eye-safe free space and POF communications.
    Proc SPIE 01/2008;
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    ABSTRACT: We have fabricated VCSELs in the visible red spectrum. The emission wavelength ranges from approximately 650 nm to 690 nm depending on application. The devices are grown on GaAs substrates by MOVPE and processed using standard VCSEL processing technology. The active layer consists of three InGaP quantum wells. The Bragg mirrors are AlGaAs/AlAs multilayer structures. The bottom mirror is n-doped, the top mirror is p-type doped. The threshold current of the devices is less than 2 mA. The maximum operating temperature is beyond 60degC. The optical output power is limited by eye-safety conditions to a maximum of 390 muW. The modulation bandwidth of the devices is in excess of 3 GHz even for low operating currents below 5 mA. This enables IEEE1394b S800 and Gigabit Ethernet transmission speed over POF as well as higher speed applications such as optical links for high definition TV. Any real application requires highly reliable devices and hence intensive life time testing of these red VCSELs has been undertaken. From aging test results applying various operating temperatures and currents we have inferred a conservative estimate for the activation energy of 0.6 eV. The 1%-time-to-failure (1%TTF) of the devices is over 100,000 hrs at use conditions. Continuous testing of more devices over thousands of operating hours is poised to improve reliability data further.
    Electronic Components and Technology Conference, 2007. ECTC '07. Proceedings. 57th; 01/2007