Jamshid Sangirov

10 Gbps Transimpedance Amplifier-Receiver for Optical Interconnects

2with power consumption of 16.9 mW at 1.3 V. The measured input-referred noise of optical TIA-Rx is 20 pA/√Hz with a 3-dB bandwidth of 6.9 GHz. The proposed TIA-Rx achieved a high gain-bandwidth product per DC power figure of merit of 408 GHzΩ /mW.

40 Gb/s optical subassembly module for a multi-channel bidirectional optical link

A 40 Gb/s bidirectional optical link using four-channel optical subassembly (OSA) modules and two different wavelengths for the up- and down-link is demonstrated. Widely separated wavelengths of 850 nm and 1060 nm are used to reduce the optical crosstalk between the up- and down-link signals. Due to the integration capabilities of silicon, the OSA is implemented, all based on silicon: V-grooved silicon substrates to embed fibers and silicon optical benches (SiOBs) to mount optical components. The SiOBs are separately prepared for array chips of photodiodes (PDs), vertical-cavity surface-emitting lasers (VCSELs), and monitoring PDs, which are serially configured on an optical fiber array for direct coupling to the transmission fibers. The separation of the up- and down-link wavelengths is implemented using a wavelength-filtering 45° mirror which is formed in the fiber under the VCSEL. To guide the light signal to the PD another 45° mirror is formed at the end of the fiber. The fabricated bidirectional OSA module shows good performances with a clear eye-diagram and a BER of less than 10(-12) at a data rate of 10 Gb/s for each of the channels with input powers of -8 dBm and -6.5 dBm for the up-link and the down-link, respectively. The measured inter-channel crosstalk of the bidirectional 40 Gb/s optical link is about -22.6 dB, while the full-duplex operation mode demonstrates negligible crosstalk between the up- and down-link.

Design of small-area transimpedance optical receiver module for optical interconnects

The development and miniaturization of electronic devices and components is pushing the system devices and their interconnecting interfaces to become even smaller. Thus, reducing the size of receiver (Rx) and transmitter (Tx) chips plays an plays an important role in designing a small-size optical modules utilized in o/e and e/o converters. Therefore, designing a small-area optical Rx may require intuitive solutions, such as building single-ended Rx and utilizing some of the advantages of differential Rx. Optical Rx should convert optical input signal to voltage output signal and provide sufficient gain and frequency operation for feeding to subsequent blocks including clock and data recovery circuit (CDR) and/or Serializer and Deserializer (SerDes). Therefore, we have designed a small-area transimpedance optical receiver (TIORx) using regulated-cascode (RGC) as an input stage which converts input photocurrent to voltage signal. The RGC block is connected to post amplifying stages to increase the overall transimpedance gain of the TIORx. The post amplifying gain stages utilizes two intersecting active feedback in order to increase the frequency operation in addition to increasing the gain of the proposed TIORx chip. The TIORx module is designed in a 0.13μm CMOS technology and works up to 10 Gbps data rate. The TIORx chip core occupies an area of 0.051mm2 with power consumption of 16.9 mW at 1.3 V. A measured 3-dB bandwidth of 6.9 GHz was obtained for the TIORx module with a transimpedance gain of 60 dBQ.

Analytical model for crosstalk analysis of optoelectronic transmitter modules for optical interconnects

In this paper, a crosstalk expression and equivalent circuit model have been proposed based on RLC line model and interconnect parameters for wire-bonded and flip-chip bonded multichannel optoelectronic modules. The analytical expression and model are accurate for computing crosstalk of interconnects used in chip packaging. In addition, full-wave simulation and experimental results from total crosstalk measurement are discussed.

Short turn-on/off time linear voltage regulator with data detector for power-aware optical interconnect system

A proposed power-aware optical interconnection system consists of a supply control voltage regulator, a receiver circuit, and a transmitter circuit. The supply control voltage regulator power consumption is 220 μA at 3.3 V and the optical receiver and transmitter has 27 mA and 64 mA at 1.8 V respectively. The transient response of supply control voltage regulator has 3.1 ns and 0.4 ns for rising and falling time, respectively.

Low-power and high-speed SerDes with new dynamic latch and flip-flop for optical interconnect in 180 nm CMOS technology

We propose a new dynamic D-latch for low-power high-speed SerDes in chip-to-chip optical interconnect. The overall SerDes circuit uses 3.6 times less number of transistors, with smaller SerDes occupying 50% less area, compared to the previous works. The SerDes operates up to 10 Gbps data rate, and the power consumption is 49.3 mW at 1.8 V, which is 30 % less power.

A performance analysis of optimized semi-blind channel estimation method in OFDM systems

Nowadays, one of the effectively used technique in wireless communication area is an orthogonal frequency division multiplexing (OFDM). In OFDM systems, channel impairments due to multipath dispersive wireless channels can cause deep fades in wireless channels. Therefore, an accurate and computationally efficient channel state information necessary when coherent detection is involved in the OFDM receiver. Hence, it is essential to have a good channel estimation method for OFDM systems in wireless communication. And normally one of the good channel estimation methods is a semi-blind channel estimation. On the other hand, the semi-blind method requires a large number of processing operations. In order to avoid the high complexity of the existing method, the semi-blind channel estimation has been optimized. At the receiver side, we calculate subspace decomposition for blind channel estimation and further to improve channel estimation we use training based technique to estimate channel state information. Next, we combine these channel estimations as semi-blind channel estimation methods and we optimized semi-blind channel estimation by choosing an optimal technique for training based channel estimation.

An enhanced semi-blind channel estimation for MIMO-OFDM systems

Abstract In wireless communication an orthogonal frequency division multiplexing (OFDM) system is efficiently used in recent years. The OFDM method in wireless channels can create deep fades, as a result of multipath dispersive spreading. Thus, a channel state information is essential when coherent detection is involved in OFDM system. Therefore, in many coherent communication systems, a good channel estimation method is necessary for OFDM receiver design. And semi-blind channel estimation is one of these good channel estimation methods. Conventionally, a semi-blind channel estimation uses least square (LS) technique. In our paper, we applied the scaled least square (SLS) to enhance the performance of the semi-blind channel estimator. The SLS requires less knowledge of the channel second-order statistics and has improved performance than the LS technique. Simulation results show that the proposed SLS semi-blind channel estimation method enhances the performance reasonably than conventional semi-blind channel estimation.

Power Saving Rx Design for Optical Modules

In this paper, a power saving optical receiver (Rx) module has been designed, fabricated using a 0.13-μm CMOS technology and demonstrated the performance with experimental results. In the Rx module, a power control block is designed to control the power of Rx according to the presence or absence of an incoming signal at the input of Rx. The Rx switches to a passive operation mode when there is no signal at Rx input. In the passive operation mode, the fabricated Rx shows a power saving efficiency of about 51%, where Rx is not receiving. When there is an input signal at Rx input, the Rx switches to an active operation mode with a system efficiency of about 97.5%. The experimental data shows that the Rx module consumes of about 67 mW at 1.3 V and power control block consumes of about 1.6 mW at 1.4 V. The measured 3-dB bandwidth of 2.56 GHz was recorded for optical Rx module. The bit error rate (BER) performance of 10−12 is achieved for the proposed optical Rx module up to 2.5 Gbps data rate with a clear eye-diagram by a very low optical input power of about −3 dBm.

10 Gbps/ch Full-Duplex Optical Link Using a Single-Fiber Channel for Signal Transmission

A 10 Gbps/ch full-duplex (simultaneous bidirectional) optical link utilizing two optical subassembly (OSA) transceiver (TRx) modules and two wavelengths, 850 and 1060 nm, for sending and receiving optical signals through a single fiber channel in a fiber array is demonstrated. Each of the OSA TRx modules consists of transmitter/receiver chips, optical fibers embedded in a V-grooved silicon substrate, two 45 ° mirrors formed in fibers, and three silicon optical benches for mounting vertical-cavity surface-emitting lasers, photodiodes (PDs), and monitoring PDs. Mirror-1 in the fiber is coated with a wavelength-filtering layer to reflect transmitted light and pass through received light. Mirror-2 deflects received light to the PD. Two OSA TRx modules were applied in an end-to-end quad small form-factor pluggable optical link for 40-Gbps operation. This optical link showed good performance with clear eye-diagrams and a BER of at <;10-12 Gbps/ch with -8-dBm input power.