Hsu-Feng Chou

High extinction ratio and saturation power traveling-wave electroabsorption modulator

An InGaAsP multiquantum-well traveling-wave electroabsorption modulator is demonstrated with high extinction ratio and modulation efficiency. By designing a strain-compensated quantum-well active region with traveling-wave design, high saturation power (>14 dBm) for >20-GHz high-speed performance (1.5 dB drop at 20 GHz) is achieved. Due to high modulation efficiency (>30 dBN for 0 to 1 V 40-dB extinction ratio in 2 V), error free 10-Gb/s operation with 1 V/sub p-p/ driving voltage is obtained. By comparing codirections and counterdirections of optical and microwave interactions, pulse generation at 40 GHz shows that the traveling-wave performance has an advantage for short pulses with high-power output, where pulsewidth as short as 4.5 ps is obtained in this kind of device.

Integrated Coherent Receivers for High-Linearity Microwave Photonic Links

In this paper, we present a coherent receiver based on an optical phase-locked loop (PLL) for linear phase demodulation. The receiver concept is demonstrated at low frequency. For high-frequency operation, monolithic and hybrid integrated versions of the receiver have been developed and experimentally verified in an analog link. The receiver has a bandwidth of 1.45 GHz. At 300 MHz, a spurious free dynamic range (SFDR) of 125 dB ldr Hz2/3 is measured.

Highly Linear Coherent Receiver With Feedback

We propose and demonstrate a novel coherent receiver with feedback for high-linearity analog photonic links. In the proposed feedback receiver, a local phase modulator tracks the phase change of the signal and reduces the effective swing across the phase demodulator without reducing the transmitted signal. The signal-to-noise-ratio is thus maintained while linearity is improved. Up to 20-dB improvement in spur-free dynamic range (SFDR) is achieved experimentally. At 3.13 mA of average photocurrent per photodiode, the measured SFDR is 124.3 dBmiddotHz2/3, which corresponds to an SFDR of 131.5 dBmiddotHz2/3 when the link is shot-noise-limited

Compact 160-Gb/s add-drop multiplexer with a 40-Gb/s base rate using electroabsorption modulators

We report on the first 40-Gb/s-based 160-Gb/s add-drop multiplexer (ADM) using a pair of standing-wave enhanced electroabsorption modulator (EAM). Direct time-domain switching is performed without interferometers or optical control pulses as required by previously reported approaches, which indicates great advantages in compactness for the EAM-based ADM. Also, a 40-Gb/s base rate is attractive in realizing a more efficient 160-Gb/s system. Error-free operation for all channels is obtained with an average power penalty as low as 1 dB.

High Output Saturation and High-Linearity Uni-Traveling-Carrier Waveguide Photodiodes

Waveguide uni-traveling-carrier photodiodes (UTC-PDs) have been fabricated and tested. Output saturation currents greater than 40 mA at 1 GHz are demonstrated for a 10 mumtimes150mum photodiode (PD). The third-order intermodulation distortion is also measured and exhibits a third-order output intercept point of 43 dBm at 20 mA and 34 dBm at 40 mA for this same PD. UTC-PDs with geometries of 5 mumtimes100 mum and 10 mumtimes100 mum are also compared and it is shown that a wider waveguide PD has improved saturation characteristics due to the lower optical power density which reduces the saturation at the front end of the device

Raman-enhanced regenerative ultrafast all-optical fiber XPM wavelength converter

The Raman gain enhancement of a regenerative ultrafast all-optical cross-phase modulation (XPM) wavelength converter (WC) is quantitatively investigated and experimentally demonstrated to operate error free at 40 and 80 Gb/s. The regenerative nature of the converter is shown by experimentally demonstrating a negative 2-dB power penalty at 80 Gb/s. It is also shown that the Raman gain greatly enhances the wavelength conversion efficiency at 80 Gb/s by 21 dB at a Raman pump power of 600 mW using 1 km of highly nonlinear fiber. An analytical theory based on nonlinear phase-shift enhancement of the fiber-effective length is presented and shows the relationship between a nonlinear enhancement and Raman gain as a function of pump power and fiber design parameters. Measured parameters are used in the analytical model, and a good fit between experiment and theory is shown for two different types of fiber: one dispersion-shifted and one highly nonlinear fiber. The ultrafast response time of Raman gain makes this technique applicable to fiber-based ultrafast WCs. In addition, the applicability to other nonlinear fiber wavelength conversion techniques is discussed.

SFDR Improvement of a Coherent Receiver Using Feedback

A novel coherent optical receiver is proposed and experimentally demonstrated by using a feedback technique capable of reducing the nonlinear distortion in a traditional receiver while retaining the signal to noise ratio.

40-Gb/s optical clock recovery using a compact traveling-wave electroabsorption modulator-based ring oscillator

Compact optical clock recovery is demonstrated by utilizing filtered and amplified photocurrent in a traveling-wave electroabsorption modulator. The 40-GHz optical clock was recovered from a 40-Gb/s optical time-division multiplexed signal and transferred to a new clock wavelength. The recovered optical clock has 500-fs timing jitter and 8-ps pulsewidth.

Two-hop all-optical label swapping with variable length 80 Gb/s packets and 10 Gb/s labels using nonlinear fiber wavelength converters, unicast/multicast output and a single EAM for 80- to 10 Gb/s packet demultiplexing

We demonstrate for the first time two hops of all-optical label swapping of variable length 80 Gb/s packets and 10 Gb/s optical labels, with unicast/multicast capability using an all-optical fiber cross-phase modulation wavelength converter.

Optical label swapping using payload envelope detection circuits

Optical label swapping of 10-Gb/s nonreturn-to-zero (NRZ) labels attached to 40-Gb/s return-to-zero payloads is demonstrated using payload envelope detection (PED) circuits based on 40-Gb/s clock recovery with nanosecond locking time. The circuits generate a digital envelope signal representing the payload location without having to process the 40-Gb/s data. The low-frequency PED signal, which is generated from the recovered 40-GHz packet clock by a radio-frequency mixer, can be utilized to erase/rewrite the label through traveling-wave electroabsorption modulators. This approach does not require active timing control to erase the label. Nearly penalty-free rewriting of a new 10-Gb/s NRZ label was demonstrated.