Philippe Rochard

Multi-Data-Rate System Performance of a 40-GHz All-Optical Clock Recovery Based on a Quantum-Dot Fabry–PÉrot Laser

Bit-error-rate assessment of a multi-rate all-optical clock recovery (OCR) based on a narrow linewidth mode-locked quantum-dot (QD) Fabry-Perot laser is presented in this letter. OCR has been achieved without external feedback. We use a QD Fabry-Perot semiconductor laser designed for 40-GHz clock extraction. We then present OCR performance with 40-, 80-, and 160-Gb/s input data signal and demonstrate that clock recovery has been obtained thanks to subharmonic locking process. Results are presented through penalty measurement using an original characterization based on recovered clock remodulation with electrical data from the transmitter. This technique allows us to evaluate the quality of the recovered clock.

Expanded single-mode fiber using graded index multimode fiber

A compact large Gaussian mode field diameter single-mode fiber is developed. This expanded single-mode fiber consists of splicing fibers with various lengths and characteristics. The principle of this optical arrangement is to excite the first mode of propagation of the multimode graded index to preserve a Gaussian field. The coupling properties are numerically analyzed, considering the effects of gap, radial offset, and tilt. The fiber connections loss between the same kinds of expanded single-mode fibers with a Gaussian mode field diameter of 18 µm is measured with an average of 0.55 dB. This large mode field diameter is preserved on a long length of fiber >20 cm.

Nondestructive method to measure coupling and propagation losses in optical guided structures

We propose and demonstrate a nondestructive method for loss measurement in optical guided structures. In the proposed approach, the device under test does not require connectors at its ends, thus making this technique available for both optical fibers and integrated optical waveguides. The loss measurement is feasible over a broad range, from low (0.2  dB/km) to high (of the order of 1  dB/mm) loss values. This method is validated through measurements performed on a microstructured holey fiber and on a photonic-crystal waveguide. The obtained results are in good agreement with theoretical calculations and measurements obtained by other approaches.