Pin PDs Research Articles

A 56-GBaud Linear Optical Receiver Hybrid Integrated with InGaAs PIN PDs

A 56-GBaud Linear Optical Receiver Hybrid Integrated with InGaAs PIN PDs

Research on full duplex FSO access system with hybrid 16PSK/256QAM-OFDM downlink and duobinary uplink signals

a 100Gbit/s novel full duplex free space optical (FSO) access system scheme is proposed and demonstrated. Using the downlink hybrid 16phase shift keying (PSK)/256quadrature amplitude modulation (QAM)-orthogonal frequency division multiplexing (OFDM) and duobinary uplink signals. In downlink branch, in-phase/quadrature-phase (I/Q) modulation based on Mach-Zehnder modulator (MZM) and coherent detection technology are adopted. Meanwhile, 0.1Terahertz (THz) wave signal generated by two independent optical sidebands beating frequency at positive intrinsic-negative photodiodes (PIN PDs) for hybrid downlink 16PSK/256QM-OFDM signals. In uplink branch, intensity modulation and direct detection (IM/DD) can achieve reduced the communication budget cost and simplified the system configuration Simulation results show that the value of bit error ratio (BER) less than hardware decision forward error correction (HD-FEC) threshold after 300 m FSO channel transmission under the different weather conditions (such as sunny, rainy and snow).

Investigation of hybrid LD/LED system for UWOC link with depth variations

Abstract In this paper, An UWOC system using a hybrid LD/LED link is proposed. A simulation was assumed to study the quality of the received optical signal with different modulation schemes such as 64-PPM, 4-QAM, NRZ-OOK, and RZ-OOK. A total of 64-PPM modulation schemes have enhanced the distance link compared with other modulation schemes. PIN and APD PDs are employed to validate the quality of the received optical signal under different water depths. Various metrics of BER, Q. factor, and data rate was introduced to assess the reliability of the hybrid LD/LED link. The simulation results show the proposed system can be achieved a good link with different water depths. The attenuation coefficient of water varies with depth and restricted the performance link distance by hybrid LD/LED link. The 64- PPM is a suitable modulation scheme for getting a long-distance link. The photodetector APD PD outperforms the PIN PD when 64-PPM and 4-QAM are applied.

(Invited) Si Waveguide-Integrated High-Speed Ge Photodetector

Silicon photonics has recently become a subject of intense interest because it offers an opportunity for low cost, low power consumption, and high bandwidth of optoelectronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects. By the integration of germanium into silicon photonics circuit, very efficient photodetection has been demonstrated for the past several years. However, higher performance with low drive voltage and small footprint has not been achieved.In this paper, we present a Si waveguide (WG)-integrated PIN-type Ge-PD (photodetector), which shows high speed of 50 GHz bandwidth with small footprint. We also compare Si waveguide-integrated PIN and Schottky Ge PDs, which showed very low dark current density with high efficiency.We fabricated two types of PIN Ge-PDs, which were evanescently coupled and butt-joint coupled with the Si WGs. The optimized evanescently coupling type of a PIN Ge-PD showed good photoresponsivity of 0.8 to 1.0 A/W and low dark current density of 0.6 nA/um2. It showed 50 GHz bandwidth at Vdc more than 3 V, and 30 GHz at 0 Vdc in case of 10 um optical coupling length. Furthermore, we developed a butt-joint type PIN Ge-PD and achieved 46 GHz bandwidth and high-efficiency with only 5 um optical coupling length.We also studied PIN and Schottky type Ge PDs. Both PIN and Schottky type Ge PDs showed good photoresponsivity of about 1.0A/W, and a low enough dark current density of 0.4 nA/um2 for the PIN Ge PD and 0.8 nA/mm2 for the Schottky Ge PD. The frequency of the 3 dB bandwidth was 40 GHz for the PIN Ge PD and 30 GHz for the Schottky Ge PD in case of 1 um-thick Ge layer. At lower dc bias voltage (Vdc), a much larger bandwidth was obtained for the PIN Ge PD. From the equivalent circuit model fitting, the Schottky Ge PD showed much larger capacitance around the zero bias voltage.The PIN Ge PD showed a larger bandwidth with decreasing Ge thickness. About 50 GHz bandwidth was obtained with a voltage more than 3 Vdc, and at even zero bias, 30 GHz bandwidth was obtained.Finally, we studied a PIN Ge PD with a small footprint and low consumption CMOS TIA circuit. To achieve a smaller footprint and larger impedance gain, we used an inverter-type TIA circuit. We demonstrated large sensitivity and high-speed response of 12.5 Gbps.

High-Speed Response of Uni-Traveling-Carrier Photodiodes

The photoresponse of a uni-traveling-carrier photodiode (UTC-PD), which is configured with a neutral narrow-gap light absorption layer and a depleted wide-gap carrier collecting layer, is investigated by small-signal analysis. Drift-diffusion model was used for analyzing carrier dynamics in the absorption layer. For accurately predicting the frequency response, a boundary condition at the edge of the absorption layer was carefully treated by taking into account the electron thermionic emission velocity. High electron mobility in the absorption layer and high drift velocity in the carrier collecting layer associated with the velocity overshoot effect are both essential for short response times. Calculations performed on InP/InGaAsP UTC-PDs with the same absorption and carrier collecting layer thicknesses show that the response can be dominated by the electron transport in the absorption layer provided that the significant velocity overshoot occurs in the carrier collecting layer. Furthermore, a UTC-PD with a quasi-field in the absorption layer can generate a several times broader bandwidth than conventional pin PDs, while maintaining a similar internal quantum efficiency.

Giga-bit rate receiver OEICs grown by OMVPE for long-wavelength optical communications

Receiver optoelectronic integrated circuits (OEICs) in which AlInAs/GaInAs HEMTs and GaInAs pin PDs were integrated monolithically on InP substrates, were studied. Good uniformity of device characteristics over a 2-inch whole wafer was obtained. Three different types of receiver circuits, i.e. high-impedance type, trans-impedance type, and straightforward termination type, were fabricated and are discussed. The sensitivity of −30.4 dBm was obtained for 1.2 Gbit/s NRZ signals from the high-impedance type OEIC, into which an equaliser was also integrated. The receiver operated up to 1.6 Gbit/s. The dynamic range of more than 23 dB was obtained using the straightforward termination type OEIC. These performances are good enough for practical use in optical communication systems operating at gigabit/s data rates.