Thomas Choi

Ultralow-Cost Optical Transceiver Modules Based on Leadframe Plastic-Package Technology

We have developed ultralow-cost optical transceiver modules based on leadframe (LF) based plastic package. The vertical-cavity surface-emitting laser (VCSEL) based transmitter shows stable optical power output with a variation of less than 0.2dB over a wide temperature range from -40degC to +105degC. Optical output eye-diagrams at 50Mbps show excellent timing performance with low jittering less than 150ps. The extinction ratio is maintained around 8dB from -40degC to +105degC. The transmitter modules show excellent reliability data including 1000 cycles of temperature cycling from -40degC to +125degC. On the receiver side, we have fabricated GaAs metal-semiconductor-metal photo detectors (MSM-PD). The MSM-PD has a lower capacitance per unit area compared to conventional pin-photodiodes. The capacitance of the MSM-PD with diameter 250mum at different bias voltages is around 0.8pF at bias voltages from 0.5V to 10V. The MSM-PD receiver shows a wide open eye diagram at 3.2Gbps. From the bit error rate curve of the receiver we interpolate a sensitivity of better than -18dBm for error rate of 10-12. We have demonstrated high speed transmission at 1.25Gbps over 10m PCS fiber with our VCSEL transmitter and MSM-PD receiver. For lower data rates and extended reach applications in low cost POF systems, we have developed Green-LED transmitters operating at 520nm wavelength. For a 40m POF system we obtain a 3.1dB wider power budget margin over the operating temperature range from 0degC to 85degC compared the red LED transmitters. The 10Mbps optical output waveforms are wide open at 25degC and 85degC

Small size fiber optic modules based on plastic packaging technology for gigabit speed video link applications

We have developed small size fiber optic modules based on plastic packaging technologies for PCS fiber systems. The transmitter contains a vertical-cavity surface emitting laser (VCSEL) operating at 850nm wavelength, an electronics driver chip, and some passive components. The package is a low cost leadframe style for through-hole or surface mounting (SMT). The SMT fiber optic transmitter is compatible with a reflow soldering process in an infra-red oven of 250degC peak temperature. With a specially designed heat shield the prototype shows a stable optical alignment performance before and after the reflow soldering. The output power of the transmitter is limited to 0.7mW to meet eye-safety class I requirements. The transmitter has an integrated coupling optics to provide loose alignment tolerances of plusmn70 mum in lateral axis for a working distance of 500mum to PCS optical fibers. The optical coupling power from the transmitter to the PCS fiber has a variation within 1dB over the wide ambient temperature range from -40degC to +105degC. This enables the usage of very low cost plastic molded connector ferrules. The receiver module contains a high speed MSM photodetector. The special design of the MSM photodetector enables high speed operation up to 3.2Gb/s in combination with a large active area for easy alignment. With two pairs of the fiber optic modules, we demonstrate a 1Gb/s video transmission over up to 15m of polymer cladded silica (PCS) optical fiber. The video link consists of a camera with an electrical S800 LVDS interface and a high resolution monitor. A pair of fiber optic cable connects the two ports replacing and extending the regular electrical cable. In contrast to the electrical cable the optical fiber is thin, light weight, and highly flexible. The high power budget margin of the link allows three in-line connectors for the 10-15m link length. For other applications a longer link length is feasible using higher bandwidth optical fiber. The VCSEL based fiber optic transmitter module has passed 3000 hours of high temperature operating life test at an operating ambient temperature of +105degC. The FOTs have also passed 1000 cycles of temperature cycling from -40degC to +125degC according to automotive requirements. The modules have passed electrostatic discharge tests at levels up to plusmn4000V under human body model and plusmn400V for machine model with no significant change in optical output power. The applications include automotive and industrial video links, home networks, and real-time surveillance systems

Highly integrated plastic package transceiver modules for large core fiber systems

We have developed fiber optic transceivers (FOT) based on leadframe and plastic molding technology for large core POF and PCS fiber systems. The leadframe style package exhibits a compact small size of 9.7mm x 6.2mm x 3.6mm. For PCS fiber system, the VCSEL based fiber optic transceivers have an operating wavelength at 850nm. The transmitter has an internal control circuit to stabilize the optical output of VCSEL and an integrated coupling optics to provide loose alignment tolerances of ±70μm in lateral axis for a working distance of 500μm to PCS optical fibers. The optical coupling power from the transmitter to the PCS fiber has a variation within 1dB over the wide ambient temperature range from -40oC to +105oC. Eye diagrams of the transceivers at 50Mbps are wide open over the normal operating temperature range from -40oC to +105oC. With a pair of VCSEL transmitter and MSM-PD receiver we achieve 1.25Gb/s transmission over 10m of PCS fiber. In a POF transmission system of 40m, over an operating temperature range from -40oC to +85oC, the fiber output power variation with the green LED transmitter is 1.5dB less than that with a similar red LED transmitter. The eye-diagrams of the green LED transmitter at 20Mbps are captured at back-to-back transmission and after 40m POF transmission.

Fiber Optic Transceivers in Surface Mount Technology for High Performance and Low Cost Optical Interconnects

We have developed plastic molded fiber optic transceiver (FOT) modules for surface mounting. The transmitter contains a vertical-cavity surface emitting laser (VCSEL) light source operating at 850nm wavelength, an electronics driver chip, and some passive components. The package is suitable for surface mounting. It shows good stability during reflow soldering in an infrared oven with a peak temperature of 250degC. With a special designed heat shield, the SMT module shows a stable optical alignment before and after the reflow soldering process. The SMT technology enables very low cost component mounting on PCB using automatic pick&place machines. The right material selection and package design is crucial for the stability of the optoelectronic module during the surface mount soldering process. The SMT module is a technology extension of our through-hole mounting FOTs. The output power of the transmitter module is limited to 0.7mW to meet eye-safety class 1 requirements. The transmitter has an internal control circuit to stabilize the optical output of VCSEL and an integrated coupling optics to provide loose alignment tolerances of plusmn70um in lateral axis for a working distance of 500um to polymer cladded silica (PCS) optical fiber with 200um core diameter. The optical coupling power from the transmitter to the PCS fiber has a variation within 1 dB over the wide ambient temperature range from -40deg C to +105degC This enables the usage of very low cost plastic molded connector ferrules. The receiver module contains a high speed MSM photodetector. The special design of the MSM photodetector enables high speed operation up to 5Gb/s in combination with a large active area for easy alignment. With two pairs of the fiber optic transceiver modules, we demonstrate a 1Gb/s video transmission over up to 15m of PCS fiber. The video link consists of a camera with an electrical S800 LVDS interface and a high resolution monitor. A pair of fiber optic cable connects the two ports replacing and extending the regular electrical cable. In contrast to the electrical cable the optical fiber is thin, light weight, and highly flexible. The high power budget margin of the link allows 3 in-line connectors for the 10-15m link length. For other applications a longer link length is feasible using higher bandwidth optical fiber. The SMT fiber optic transceivers enable new low cost applications in automotive, industrial control, and home networking. The technology can compete with electrical solutions on performance and cost and can outperform it on cable flexibility and EMI immunity

Active components for ultra-low-cost optical interconnects

Low cost optical components enable new emerging applications for short distance interconnects. We developed novel VCSEL transceiver modules based on electronics-style plastic packages for large core PCS fiber systems. The transmission data rate is 500Mbps over a wide ambient temperature range from -40°C to 105°C. For lower data rates we developed green LED based transmitters for extended reach applications using POF. On the receiver side MSM photodetectors exhibit a high sensitivity of -18dBm at a data rate of 3.2Gbps. The large area MSM receivers are essential components for high speed large core optical fiber links.

A 65nm 1.2V 16-bit audio codec sigma-delta DAC with headphone driver

This paper reports the measured results of a 16-bit audio codec sigma-delta (Σ-Δ) DAC including a class AB headphone driver, implemented in a 65nm process. The DAC operates with a single 1.2V supply voltage and a 256 times over-sampling ratio, achieving a Total Harmonic Distortion (THD) of •61dB and a Signal-to-Noise Ratio (SNR) of 93dB.

A 65nm 1.2V 16-bit audio codec sigma-delta ADC in 2-2 MASH architecture with temperature-compensated biasing

A 16-bit audio codec sigma-delta (Σ-Δ) ADC including a decimation filter, implemented in a 65nm process, is reported measured results. The ADC operates with a 1.2V supply voltage and a 256 times over-sampling, achieving a Spurious-free Dynamic Range (SFDR) of 70dB. The 2-2 MASH architecture has been employed to reduce the required capacitor ratio for improved matching. A temperature compensation scheme is also included in the biasing circuit to limit the power consumption at high temperatures.

Ultra small form factor plastic package transceiver modules for large core fiber systems

We have developed ultra small form factor fiber optic transceiver (FOT) modules using plastic packaging technologies for large core fiber systems such as plastic optical fiber (POF) and poler cladded silica (PCS) fiber systems. The 850 nm VCSEL based transmitter can operate from Mbps to Gbps depending on electrical design. An internal control circuit stabilizes the optical output power to within 0.5 dB variation over a wide ambient temperature range from -40degC to +125degC. Eye diagrams at 50 Mbps are wide open over the normal operating temperature range from -40degC to +105degC. The extinction ratio is larger than 10 dB and the uncorrelated jitter is less than 150 ps. For 50 Mbps data rate, the fiber optic receiver module consists of a Si-pin photodetector (PD) and receiver IC. The eye diagrams at 50 Mbps and -24 dBm OMA input are wide open over the entire temperature range from -40degC to +105degC. The uncorrelated jitter is less than 800 ps. A sensitivity of -34 dBm optical modulation amplitude is obtained for a BER equals to 1E-9. For high data rates up to the Gbps range, a GaAs metal-semiconductor-metal (MSM) PD is used in the receiver module. With a pair of VCSEL transmitter and MSM-PD receiver we achieve 1.25 Gbps transmission over 10 m of PCS fiber. The leadframe style package exhibits a compact small size of 9.7mm times 6.2mm times 3.6mm. It provides loose alignment tolerances of plusmn100 mum in lateral axis for a working distance of 500 mum to a large core PCS optical fiber. The transmitter module is highly reliable and stable over 1000 temperature cycles from times40degC to +125degC and also over 1000 hours at 85degC/85% damp heat condition

Gb/s transmission over PCS-fiber with ultra small form factor plastic package transceivers

We have developed ultra small form factor plastic package fiber optic transceivers which are designed for large core fiber system (PCS-fiber, PF-POF). The VCSEL based fiber optic transmitter exhibits an output power stability within 0.5dB over an operating temperature from -40°C to +105°C. The fiber optic receiver consists of a GaAs MSM-photodetector with a large active area and high bandwidth. Giga bit transmission over a 10m PCS-fiber is demonstrated with the transceivers. The modules are applicable to automotive, consumer electronics, home networking, and datacom applications.

Plastic packaging of VCSEL-based fiber optic transceivers for PCS fiber systems

We have developed VCSEL based fiber optics transceivers for PCS fiber systems. The PCS fiber has a core diameter of 200μm. The relatively large diameter enables the usage of low cost optical connectors for the fiber link and provides wide alignment tolerances. The measured lateral and longitudinal 3dB coupling tolerances are ±100μm and 500μm, respectively. The VCSEL is integrated with an electronics driver chip and some passive electronics components on a leadframe structure before plastic encapsulation. The hybrid integration on the leadframe enables batch processing to increase throughput and lower manufacturing cost. No full-hermetic sealing is required for the VCSEL chosen. The variation of optical output power is less than 0.2dB from -40°C to 105°C. Eye diagrams show wide open eyes at a data rate of 500Mbit/s at wide temperature range up to 105°C. The technology can go up to data rates in the Gbit/s range, but this is currently not required for the target applications. The module is reliable over 1000 temperature cycles from -40°C to 125°C. For the receiver side we developed high speed MSM photodetectors. The large area MSM photodetectors relax the coupling alignment tolerance to the core of the optical fiber for 80μm and 4000μm in lateral axis and longitudinal axis, respectively. The MSM photodetector is capable of data rates of 3.2Gb/s. At this high speed the sensitivity is better than -18dBm for the MSM photodetector co-packaged with a suitable transimpedance amplifier (TIA).