Intel/Agilent OE Group Karen Cano Scott Henderson Di Qian

PART I. Design Analysis VCSEL - Honeywell PIN Photo-diode - Lasermate PARTII. Constructing & Testing

Keeping track of Amps & Watts

Design Overview

Honeywell VCSELs HFE Slope Efficiency 0.04 mW/mA I threshold mA HFE Slope Efficiency 0.15 mW/mA I theshold mA

Link Budget Analysis of current and power throughout the system, starting at the TX and ending at the RX or trans-impedance amplifier.

Losses Not all of the light emitted by the VCSEL will reach the PD. Losses are incurred from the fiber and the SC connectors.

At the PD Side Once the losses have been calculated into the output power range, this new range of power is to be converted back into current. When the power or light hits the PD, it is multiplied by the responsivity of the PD, expressed in A/W. This value is the current coming out of the PD and into the trans-impedance amp.

At the RX Side The current coming out of the PD has to be large enough to drive the trans-impedance amp, which takes at least 80 uA.

Honeywell Option #1 I th = 6 mA DC bias of laser = 6 (1.2) = 7.2 mA Slope efficiency 0.04 mW/mA Power output at DC bias = 0.04 * 7.2 = mW Max TX modulation current.300 mA Power output at TX modulation current = 04 * 30 =1.2 mW Range of emission of light coming from the laser (lossless)= mW Losses3dB or 1/2 output power Range of emission of light coming from the laser (with losses)= mW Responsivity of lasermate's PD = 0.35 A/W Min. current from PD = W * 0.35 A/W= 50.4 micro Amps Max current from PD =.0006 W * 0.35 A/W =210 micro Amps Table 1. Link budget for low slope efficiency VCSEL (HFE ).

Honeywell Option #2 I th 6 mA DC bias of laser = 6 (1.2) =7.2 mA Slope efficiency 0.15mW/mA Power output at DC bias = 7.2 * 0.15 =1.08 mW Max TX modulation current.300 mA Power output at TX modulation current =.15 * 30 =4.5 mW Range of emission of light coming from the laser (lossless)= mW Losses3dB or 1/2 output power Range of emission of light coming from the laser (with losses)= mW Responsivity of lasermate's PD = 0.35 A/W Min. current from PD = W * 0.35 A/W =189 micro Amps Max current from PD = W * 0.35 A/W= 787 micro Amps Table 2. Link budget for high slope efficiency VCSEL (HFE ).

In Conclusion Prefer VCSEL with higher slope efficiency because it can drive the trans-impedance amplifier. More importantly, it can do this with the same amount of input current that is needed for the other VCSEL. If the price difference is not too significant, this VCSEL is the most reliable option.

Construction and Testing Interface optical components with Maxim Extensive testing to meet standards Develop more optimal design utilizing newly ordered VCSEL and PD Repeat testing procedures

Interfacing Purchased Components Matching spec with Maxim Attaching new parts to board to connect to test board Finalizing the setup by utilizing the test-bed BERT,Techtronix7000 Maxim Test Board Schematic

Optimizing Circuit Design Minimizing inductors and component quantities in general Utilizing existing schematics and general EE knowledge Soldering followed by repeated testing Intel/Agilent PC Interface Card

Conclusion Securing satisfactory components –VCSEL, PD Interfacing with the Maxim test board –SMA to SMA, soldering for opto-board Testing for standard compliant performance –BERT, Techtronix 7000 New design using purchased components Constructing and testing new design