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Optical devices

Enhancement of optical devices and systems performance for context driven applications

  • Faculty D. Erasme, R. Gabet, P. Gallion, C. Gosset, F. Grillot, Y. Jaouën

Cost effective high modulation bandwidth sources for access and metro networks

Providing higher bit rates, reaching longer distances and maintaining compatibility with the deployed standards are the main features of metro and specially access networks, which also have to cope with challenges related to the low cost, the small packaging and the reduced energy consumption of optical components. Optical sources for access, metro and radio-over-fiber networks must combine integration for both light generation and modulation. The ANR-MODULE project dealt with a novel integrated electro-absorption modulated laser (EML) with a dual-modulation access i.e. modulation on both the laser and the electro-absorption modulator acting conjointly on the amplitude and the phase of the emitted optical signal. This technique allows single-side-band modulation and thus immunity to fiber dispersion impairment. Record transmission ranges have been achieved in NRZ at 10, 20, 25 and 40 Gbit/s and in OFDM at 11 Gbit/s. Within the scope of the FUI-TRILOB project, we investigated another optical source consisting of an EML monolithically integrated with a semiconductor optical amplifier. Here again record transmissions were demonstrated at 10 Gbit/s. In collaboration with 3-5 labs, we investigated the potentialities of reflective SOA (RSOA) mainly for access network applications. Finally, novel device architectures including feed-back lasers and optically-injected laser and self-seeded cavities were studied showing widely enhanced bandwidth and reduced phase amplitude coupling. A powerful new modelling tool for semiconductor lasers has been developped. Within our investigation of access network solutions, we have proposed a novel decentralized scheme supporting multiple optical Private Networking (PN) over ring-based Passive Optical Network (PON) taking benefit of asynchronous OCDMA technique. The network scalability and throughput performance of the proposed scheme are analyzed.

Multi-Mode Interference coupler based switching and optical orthogonal transforms

We have analyzed the principle and the implementation of optical switching, Hadamard transform and discrete Fourier transform based on Multi Mode interference (MMI) devices in association with variable phase shifter array. The approach points out the possibility to achieve the higher order Hadamard transform using simple 2D structures and provides a possible solution for all optical CDMA systems.

Advanced characterization techniques for photonic devices

Optical Low Coherence Reflectometry (OLCR) is a unique investigation tool for the study and the characterization of new photonic components. Over the past four years, we particularly studied the impact of disorder on the propagation of photonic crystal waveguide modes. In 2009 we produced an article displaying the many capabilities of OLCR for the characterization of specialty fibers. For the FUI CHRONOS project devoted to the study of long Bragg grating manufacturing (1 m), the limits of OLCR set-up led us to develop a new characterization technique based on studying the emitted blue luminescence when the grating is irradiated by a UV beam. Finally, we are currently looking on how to implement a new technology to measure precisely the PDL and the chromatic dispersion on ultra-fine filters (width about 50 pm, slope about 800 dB/nm) in relation with the SME Yenista through a CIFRE PhD.

Associated experimental means and novel characterisation concepts

Testing optical device behaviour in communication system architectures requires high-bit-rate transmission platforms such as those mentioned in the previous paragraph (PENSER 100GIGA). In addition, measuring the complex (amplitude and phase) aspect of a modulated optical signal is crucial when one needs to assess its propagation in particular along length of dispersive optical fibers. Small-signal modulated waveform can be analysed using a dispersive element. Generalisation and analysis of this standard method was published. On the other hand a new large signal measurement method has been designed and applied to test the optical sources mentioned above

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