The 8×10 GHz Receiver Optical Subassembly Based on Silica Hybrid Integration Technology for Data Center Interconnection

An 8×10 GHz receiver optical sub-assembly （ROSA） consisting of an 8-channel arrayed waveguide grating （AWG） and an 8-channel PIN photodetector （PD） array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain fiat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimentM results show that the single channel I dB bandwidth of AWG ranges from 2.12nm to 3.06nm, the ROSA responsivity ranges from 0.097 A/W to 0.158A/W, and the 3dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

A 58-dBΩ20-Gb/s inverter-based cascode transimpedance amplifier for optical communications

This work presents a high-gain broadband inverter-based cascode transimpedance amplifier fabricated in a 65-nm CMOS process.Multiple bandwidth enhancement techniques,including input bonding wire,input series on-chip inductive peak-ing and negative capacitance compensation,are adopted to overcome the large off-chip photodiode capacitive loading and the miller capacitance of the input device,achieving an overall bandwidth enhancement ratio of 8.5.The electrical measure-ment shows TIA achieves 58 dBΩup to 12.7 GHz with a 180-fF off-chip photodetector.The optical measurement demonstrates a clear open eye of 20 Gb/s.The TIA dissipates 4 mW from a 1.2-V supply voltage.

A 26-Gb/s CMOS optical receiver with a reference-less CDR in 65-nm CMOS

This paper presents a 26-Gb/s CMOS optical receiver that is fabricated in 65-nm technology. It consists of a tripleinductive transimpedance amplifier(TIA), direct current(DC) offset cancellation circuits, 3-stage gm-TIA variable-gain amplifiers(VGA), and a reference-less clock and data recovery(CDR) circuit with built-in equalization technique. The TIA/VGA frontend measurement results demonstrate 72-dB? transimpedance gain, 20.4-GHz-3-dB bandwidth, and 12-dB DC gain tuning range. The measurements of the VGA’s resistive networks also demonstrate its efficient capability of overcoming the voltage and temperature variations. The CDR adopts a full-rate topology with 12-dB imbedded equalization tuning range. Optical measurements of this chipset achieve a 10-12 BER at 26 Gb/s for a 2;-1 PRBS input with a-7.3-dBm input sensitivity. The measurement results with a 10-dB @ 13 GHz attenuator also demonstrate the effectiveness of the gain tuning capability and the built-in equalization. The entire system consumes 140 mW from a 1/1.2-V supply.

Sensitivity analysis of an HgCdTe based photovoltaic receiver for long-wavelength free space optical communication systems

We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigorous noise model of the receiver has been developed for this purpose.We calculate the total noise and sensitivity of the receiver.The front-end of the receiver exhibits a sensitivity of -45 dBm at a bit rate of 1 Gb/s and -30 dBm at a bit rate of 10 Gb/s,and the total mean-square noise curren t〈i2n〉=5×10-15 A2 at a bit rate of 1 Gb/s an d〈i2n〉 =10-12 A2 at a bit rate of 10 Gb/s,and a 3-dB bandwidth of 10 GHz.

PIM Application Based on Client/Server Architecture

An equivalent noise model of optical receiver amplifiers as shown in Fig.1 has been given in many fiber optical communication literatures. It is proved in this paper that this equivalent noise model is neither equivalent to the original one nor measurable. The main reason is that the position of the input impedance in this noise model is not the same with its in the typical noise model,but the same S vn , S in with the typical noise model are used. So the equivalent noise model above is wrong and is not fit to be taken into application.

Characterization of Blue-Green Light Non-Line-of-Sight Transmission in Seawater

The blue-green light in the 450 nm to 550 nm band is usually used in underwater wireless optical communication (UWOC). The blue-green light transmission in seawater is scattered by the seawater effect and can achieve communication in non-line-of-sight (NLOS) transmission mode. Compared to line-of-sight (LOS) transmission, NLOS transmission does not require alignment and can be adapted to various underwater environments. The scattering coefficients of seawater at different depths are different, which makes the scattering of light in different depths of seawater different. In this paper, the received optical power and bit error rate (BER) of the photodetector (PD) were calculated when the scattering coefficients of blue-green light in seawater vary from large to small with increasing depth for NLOS transmission. The results show that blue-green light in different depths of seawater in the same way NLOS communication at the same distance, the received optical power and BER at the receiver are different, and the received optical power of green light is greater than that of blue light. Increasing the forward scattering coverage of the laser will suppress the received optical power of the PD, so when performing NLOS communication, appropriate trade-offs should be made between the forward scattering coverage of the laser and the received optical power.

4 × 20 GHz silica-based AWG hybrid integrated receiver optical sub-assemblies

Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating（AWG） with 2% refractive index difference and a four-channel top-illuminated positive-intrinsicnegative photodetector（PD） array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 Gb E data center interconnections.

A 40 Gbit/s fully integrated optical receiver analog front-end in 90 nm CMOS

A fully integrated 40 Gbit/s optical receiver analog front-end （AFE） including a transimpedance amplifier （TIA） and a limiting amplifier （LA） for short distance communication is described in this paper. The proposed TIA employs a modified regulated cascode （RGC） configuration as input stage, and adopts a third order interleaving active feedback gain stage. The LA utilizes nested active feedback, negative capacitance, and inductor peaking technology to achieve high voltage gain and wide bandwidth. The tiny photo current received by the receiver AFE is amplified to a single-ended voltage swing of 200 mV（p-p）. Simulation results show that the receiver AFE provides conversion gain of up to 83 dBΩ and bandwidth of 34.7 GHz, and the equivalent input noise current integrated from 1 MHz to 30 GHz is about 6.6 μA（rms）.

High performance power-configurable preamplifier in a high-density parallel optical receiver

A power-configurable high performance preamplifier was implemented in standard 180-nm CMOS technology for 12 × 10 Gb/s high-density ultra-high speed parallel optical communication system. With critical limitations on power consumption, area and fabrication cost, the preamplifier achieves high performance, e.g. high bandwidth, high trans-impedance gain, low noise and high stability. A novel feed-forward common gate （FCG） stage is adopted to alleviate contradictions on trans-impedance gain and bandwidth by using a low headroom con- suming approach to isolate a large input capacitance and using complex pole peaking techniques to substitute induc- tors to achieve bandwidth extension. A multi-supply power-configurable scheme was employed to avoid wasteful power caused by a pessimistic estimation of process-voltage-temperature （PVT） variation. Two representative sam- ples provide a trans-impedance gain of 53.9 dBf2, a 3-dB bandwidth of 6.8 GHz, a power dissipation of 6.26 mW without power-configuration and a trans-impedance gain of 52.1 dBg2, a 3-dB bandwidth of 8.1 GHz, a power dis- sipation of 6.35 mW with power-configuration, respectively. The measured average input-referred noise-current spectral density is no more than 28 pA/√Hz. The chip area is only 0.08 x 0.08 mm2.

VCO clock synchronization loop combined with dispersion equalization in optical coherent receivers

In optical coherent receivers,the timing error detector （TED） in synchronization loop can not work normally when signal is distorted by large dispersion.This paper proposes a novel clock synchronization scheme which adds a butterfly-structured adaptive equalizer to the loop to fulfill synchronizations,equalizations and polarization de-multiplexing of two polarization states simultaneously under the control of single voltage-controlled oscillator （VCO）.Simulink simulation demonstrates the rationality and the feasibility of the combined loop with single VCO.

Low-Cost High-Performance 10 G Transmitter and Receiver Optical Subassembly

We describe briefly here the recent R&D activities in the optical subassembly packaging technologies at the Hong Kong Applied Science and Technology Research Institute (ASTRI). We have designed, developed and prototyped multiple of low-cost high performance packages for serial and parallel transmitters and receivers, in particular, the novel chip-in-plastic (CiP) package designed for 10G serial transmission for data communications.

A 1.5Gb/s monolithically integrated optical receiver in the standard CMOS process

A monolithically integrated optical receiver, including the photodetector, has been realized in Chartered 0.35μm EEPROM CMOS technology for 850 nm optical communication. The optical receiver consists of a differential photodetector, a differential transimpedance amplifier, three limiting amplifiers and an output circuit. The experiment results show that the receiver achieves an 875 MHz 3 dB bandwidth, and a data rate of 1.5 Gb/s is achieved at a bit-error-rate of 10-9. The chip dissipates 60 mW under a single 3.3 V supply.

A monolithic,standard CMOS,fully differential optical receiver with an integrated MSM photodetector

This paper presents a realization of a silicon-based standard CMOS,fully differential optoelectronic integrated receiver based on a metal–semiconductor–metal light detector（MSM photodetector）.In the optical receiver, two MSM photodetectors are integrated to convert the incident light signal into a pair of fully differential photogenerated currents.The optoelectronic integrated receiver was designed and implemented in a chartered 0.35μm, 3.3 V standard CMOS process.For 850 nm wavelength,it achieves a 1 GHz 3 dB bandwidth due to the MSM photodetector’s low capacitance and high intrinsic bandwidth.In addition,it has a transimpedance gain of 98.75 dBΩ, and an equivalent input integrated referred noise current of 283 nA from 1 Hz up to–3 dB frequency.