Michel Joindot

Saturable-Absorber-Based Phase-Preserving Amplitude Regeneration of RZ DPSK Signals

We experimentally investigate a new generation of multiple-quantum-well semiconductor saturable absorber for all-optical phase-shift-keying signal regeneration. The device under study exhibits a reflectivity which decreases when the input signal power increases. This characteristic can be seen as a power limiting function which could be used for phase-preserving amplitude noise reduction, hence preventing from nonlinear phase noise accumulation along a transmission link. The device efficiency is demonstrated at 42.7 Gb/s; a fiber launched power margin of 2 dB and receiver sensitivity improvement up to 5.5 dB are obtained.

10 Gbit/s PON demonstration using a REAM-SOA in a bidirectional fiber configuration up to 25 km SMF

A REAMSOA chip is characterized as part of an ONU in single-pass and then bidirectional upstream 10 Gbit/s PON configurations. Chromatic dispersion and Rayleigh backscattering impacts are assessed.

Up to 425 GHz all optical frequency down-conversion clock recovery based on quantum dash Fabry-Perot mode-locked laser

We demonstrate that quantum-dash mode-locked laser can perform all optical frequency down-conversion clock recovery up to 425 GHz. We measured 0.3 dB penalty on the optical recovered clock for 170 Gbit/s signal.

Up to 427 GHz All Optical Frequency Down-Conversion Clock Recovery Based on Quantum-Dash Fabry–Perot Mode-Locked Laser

This paper reports on all optical frequency down conversion clock recovery based on Quantum-Dash Fabry-Perot mode-locked laser diode (QD-MLLD). A first section is dedicated to the generation of a tunable repetition rate pulse source based on a first QD-MLLD. The principle is to select three lines in the QD-MLLD spectrum with a filtering technique; the lines spacing are properly chosen to generate the desired repetition rate. In this paper, a frequency of 427 GHz was reached and observed with an optical sampling oscilloscope. Moreover, an encoded 170.8 GHz pulse source was characterized showing no penalty in comparison with our reference obtained by Optical Time Division Multiplexing (OTDM), which confirms the quality of the optical clock. In a second section, we show a clock frequency down conversion based on a second QD-MLLD, which is optically injected by a pulse source, whose repetition rate is 10 times higher than its self pulsating frequency. The 42.7 GHz down converted clock is then encoded and analyzed showing no penalty in comparison to a standard 42.7 Gbit/s reference, demonstrating its quality. Finally, in a third section, we demonstrate sub-harmonic clock recovery with a QD-MLLD, when a data stream is injected. We measure a penalty of 0.3 dB when compared to a standard 42.7 Gbit/s reference.

All-Optical 2R Regeneration With a Vertical Microcavity-Based Saturable Absorber

This paper gives an overview of recent demonstrations of optical 2R regeneration achieved by vertical microcavity mirror-based multiple-quantum-well saturable absorber (SA). The potential of the device to perform wavelength division multiplexing regeneration is first demonstrated through the first pigtailed SA chip implemented with eight independent fibers using a cost effective coupling technique. The cascadability and wavelength tunability assessment of this module associated with a power limiter fiber-based function has been experimentally demonstrated at 42.6 Gbit/s. Because this method of power limiting is not a suitable solution for all-optical multichannel 2R regeneration, a new SA structure allowing a power limiting function was proposed. We describe and characterize such a structure in this paper. This new SA opens the door to a complete passive all-optical 2R regeneration relying upon a single technology, as shown in this paper through the use of two SA: SA.0 for extinction ratio enhancement and SA.1 for high-power level equalization allowing receiver sensitivity (up to 3.5 dB) and Q-factor (up to 1.4 dB) improvement for a RZ signal at 42.6 Gbit/s. The limitation of SA.1 when the regenerator must be cascaded a large number of times is also described, leading to the observation that SA.1 should be more suitable for phase encoded formats that are more spectrally efficient than ON-OFF keying formats. A SA.1 used as a phase-preserving amplitude regenerator in a 42.6 Gbit/s RZ differential quadrature phase-shift keying transmission system is, therefore, assessed . A fiber launched power margin of 2 dB and a receiver sensitivity improvement of 5.5 dB are obtained. Finally, we use, for the first time an SA.1 as a phase-preserving amplitude regenerator of RZ differential quadrature phase-shift keying signals. The regenerator is assessed in a recirculating loop at 28 Gbaud. The system tolerance to nonlinear phase noise is enhanced by 3 dB and the distance improvement factor was 1.3 for a bit error rate = 10-4.

Self-phase modulation-based 2R regenerator including pulse compression and offset filtering for 42.6 Gbit/s RZ-33% transmission systems

We report on the experimental and theoretical study of a self-phase-modulation-based regenerator at 42.6 Gbit/s with a return-to-zero 33% format. We point out some detrimental effects such as intrachannel interactions and Brillouin scattering. An efficient solution, relying on a self-phase-modulation-based pulse compressor in combination with the regenerator, is proposed to overcome these detrimental phenomena. The experimental demonstration shows the effectiveness of a wavelength-transparent regenerator at 42.6 Gbit/s with a sensitivity-improvement of more than 5 dB and an eye-opening improvement of 2.3 dB in a back-to-back configuration, as well as a 10 times maximum transmission distance improvement for a BER of 10(-4).

Patterning Effects in All-Optical Clock Recovery: Novel Analysis Using a Clock Remodulation Technique

In this paper, we present a complete study of the pattern sequence length influence in the optical clock recovery (OCR) process using passive filtering. For this analysis, we use a commercial Fabry-Perot filter (FPF) in front of a semiconductor optical amplifier. A 40-GHz optical clock is then recovered from an optical data stream at 40 Gbit/s. The recovered clock (RCK) quality relies on an original technique based on the remodulation by the optical clock with electrical data. Then we perform two studies in order to explore the dependency of the RCK on patterning effects: first, we carry out a numerical simulation of the tandem filter and amplifier, in order to study its performance as an OCR process. The impact of each component of the clock recovery process is clearly observable via the quality of the remodulated clock. Second, we experimentally study the sensitivity of the OCR to the incoming pattern length using phase noise and bit-error-rate measurements in an optical communication system environment. This study allows an in-depth study of this simple and frequently used OCR configuration, and outlines some limitations of the technique, linked to the compatibility between the finesse of the FPF, the pattern length, and the general optical communication system properties.

2R Optical Regeneration combining XGC in a SOA and a Saturable Absorber

Wavelength-preserving 2R-regeneration based on saturable-absorber and cross-gain-compression in gain-saturated SOA is experimentally demonstrated for NRZ-10-Gbit/s signals. The regenerator noise resistance is proven in a recirculating loop with noise loading.

All-optical sampling and spectrographic pulse measurement using cross-absorption modulation in multiple-quantum-well devices

The application of cross absorption modulation for optical sampling and phase sensitive pulse measurement is presented. Both a commercial 40 GHz electroabsorption modulator and a vertical microcavity saturable absorber are used to sample a 2 ps pulse train at 40 GHz. The modulator was then used to make cross-absorption modulation based frequency-resolved optical gating (FROG) measurements. The results were verified by comparison with a commercial optical sampling oscilloscope and the more standard second harmonic generation FROG technique.

IQ imbalance compensation based on maximum SNR estimation in coherent QPSK systems

We present a simple alternative method for the compensation of quadrature imbalance in optical quadrature phase-shift-keying (QPSK) coherent systems. The method is based on the determination and the compensation of the phase mismatch by the introduction of a relevant signal-to-noise ratio metric. The principle is validated numerically and the algorithm is validated experimentally through bit-error-rate (BER) and error vector magnitude (EVM) measurements. A 20 Gb/s optical QPSK experiment reveals a good agreement of the proposed method with the Gram-Schmidt orthogonalization procedure (GSOP). Moreover, the robustness of both methods was verified with up to 30° phase misalignment by comparing the signal after phase imbalance compensation to that without compensation. A 10% reduction of EVM is achieved with our method for a high phase misalignment of 30°.