We report a visible-light wireless point-to-point communication link operating at 513 Mbit/s gross transmission rate (net Mbit/s). The bit-error ratio of the uncoded data was smaller than for an illumination level of lx. The link was based on a commercial thin-film high-power phosphorescent white LED, an avalanche photo diode, and off-line signal processing of discrete multitone signals. Quadrature-amplitude modulation, bit- and power-loading, as well as symmetrical clipping were successfully employed in pushing the gross transmission rate beyond 500 Mbit/s. Adaptation of the clipping level increased the data rate only by 2%, while simulations predicted an enhancement of 20%. Obstacles towards higher data rates as well as potential remedies are discussed. We predicted that data rates of over 1 Gbit/s can be achieved with the same setup and under the same experimental conditions if these obstacles are overcome.

513 Mbit/s Visible Light Communications Link Based on DMT-Modulation of a White LED

The performance of advanced modulation schemes for spectrally efficient data transmission is reviewed, targeting short-range intensity-modulated optical channels with direct detection. Hereby, the focus lies on the performance of multilevel pulse-amplitude modulation combined with electronic equalization and, as an alternative modulation scheme, discrete multitone. A comprehensive statistical analysis of clipping noise is presented and exact expressions for the performance of symmetrically clipped discrete multitone are derived. It is shown that the clipping noise is impulsive and obeys a generalized Laplace distribution. The bit-error probability due to clipping is studied in detail, and it is found that the impact of clipping noise is reduced for an increasing number of subchannels. Finally, the optical link margins of multilevel pulse-amplitude modulation in combination with electronic equalization and that of discrete multitone in combination with margin-adaptive bit loading are compared. It is found that even symmetrically clipped discrete multitone suffers from its large crest factor in the peak-power-limited channel and that, in many instances, pulse-amplitude modulation provides higher link margins for the same target bit-error probability.

Advanced Modulation Schemes for Short-Range Optical Communications

Narrow linewidth lasers have many applications, such as higher order coherent communications, optical sensing, and metrology. While semiconductor lasers are typically unsuitable for such applications due to relatively low coherence, recent advances in heterogeneous integration of III-V with silicon have shown that this is no longer true. In this tutorial, we discuss in-depth techniques that are used to drastically reduce the linewidth of a laser. The heterogeneous silicon-III/V platform can fully utilize these techniques, and fully integrated lasers with Lorentzian linewidth on the order of 100 Hz and tuning range of 120 nm are shown.

/pdf/tutorial-on-narrow-linewidth-tunable-semiconductor-lasers-8dhr4seov8.pdf

Tutorial on narrow linewidth tunable semiconductor lasers using Si/III-V heterogeneous integration

Coherent optical transmission systems offer enhanced possibilities concerning multilevel modulation and the electronic compensation of transmission impairments. One of the key components in a homodyne in-phase/quadrature (IQ) receiver is a 2 times 4 90deg hybrid. However, this component is only commercially available in a form that requires an additional active control loop. This paper presents the different possible alternatives for the realization of the 2 times 4 90deg hybrids and discusses their availability and properties, as well as the practical implementation considerations

Options, feasibility, and availability of 2 /spl times/ 4 90/spl deg/ hybrids for coherent optical systems

Two different laser phase noise measurement techniques are compared. One of these two techniques is based on a conventional and low-cost delay line system, which is usually set up for the linewidth measurement of semiconductor lasers. The results obtained with both techniques on a high-spectral-purity laser agree well and confirm the interest of the low-cost technique. Moreover, an extraction of the laser linewidth using computer-aided design tools is performed.

https://hal.archives-ouvertes.fr/hal-00609221/document

Phase noise measurement of a narrow linewidth CW laser using delay line approaches

Several techniques for phase noise PSD measurement of continuous wave (CW) lasers to be used in coherent transmission systems are analyzed. Between them, we evaluate two novel techniques. The first employs a homodyne optical phase-locked loop, while the second uses a signal source analyzer. Experimental results obtained by these two methods are compared with classical linewidth measurement methods like self-heterodyne and Michelson interferometer. Limits and accuracy of each method are discussed. Furthermore, the comparison shows that, for coherent transmission system applications, only a subset of the analyzed methods is useful for laser phase noise characterization.

/pdf/narrow-linewidth-cw-laser-phase-noise-characterization-2ynwgsjzcd.pdf

Narrow Linewidth CW Laser Phase Noise Characterization Methods for Coherent Transmission System Applications

A short overview on Optical Phase locking techniques and a detailed description of the Phase Locking technique based on Sub-Carriers modulation is presented. Furthermore, a novel Single Side Sub-Carrier-based Optical Phase Locked Loop (SS-SC-OPLL), with off the shelf optical components, is also presented and experimentally demonstrated. Our new method, based on continuous wave semiconductor lasers and optical single side sub-carrier modulation using QPSK LiNbO(3) modulator, allows a practical implementation with better performance with respect to the previously proposed OPLL circuits, and permits an easy use in real time WDM signal coherent demodulation.

Optical Phase Locking techniques: an overview and a novel method based on Single Side Sub-Carrier modulation

We present our prototype solution for transmitting 100 Mb/s Ethernet data over large core (1 mm) step-index polymer optical fiber (POF), as one of the final results of the EU-funded project POF-ALL. The system is demonstrated over a record maximum distance of 275 m, largely outperforming CAT-5 systems and currently commercially available POF media converters. These results let us envision POF deployment for home networking and industrial automation and in general for all those environments in which ease of installation, rugged solution, low-cost and electromagnetic compatibility issues are requested.

/pdf/100-mb-s-ethernet-transmission-over-275-m-of-large-core-step-a8rvlkolra.pdf

100 Mb/s Ethernet Transmission Over 275 m of Large Core Step Index Polymer Optical Fiber: Results From the POF-ALL European Project

The analysis of a subcarrier optical phase-locked loop (SC-OPLL) is carried out in order to optimize phase-locking performance. A new parameters optimization procedure, useful for OPLL design, is demonstrated theoretically and experimentally. An SC-OPLL based on this procedure has been realized, so a pilot carrier SC-OPLL and a nonlinear SC-OPLL optical receiver have been experimentally constructed and tested. An 8B/10B line coding is employed for pilot carrier SC-OPLL receiver in order to improve performance and a new architecture of decision-driven PLL is experimentally demonstrated.

/pdf/design-analysis-and-experimental-testing-of-bpsk-homodyne-3gdxpgz7pb.pdf

Design, Analysis and Experimental Testing of BPSK Homodyne Receivers Based on Subcarrier Optical Phase-Locked Loop

While ultrahigh-baud-rate optical signals are effective for extending the transmission distance of large capacity signals, they also reduce the number of wavelengths that can be arranged in a band because of their wider bandwidth. This reduces the flexibility of optical path configuration in reconfigurable optical add/drop multiplexing (ROADM) networks. Particularly in colorless, directionless and contentionless (CDC)-ROADM, the effect reduces the add/drop ratio at a node. Multiband ROADM systems are an effective countermeasure for overcoming this issue, but they make the node configuration more complicated and its operation more difficult. In this paper, we analyze the challenges of C + L band CDC-ROADM and show that optical switch devices that operate over multiple bands are effective in meeting them. For this purpose, we built a C + L band CDC-ROADM node based on C + L band wavelength-selective switches and multicast switches and confirmed its effectiveness experimentally. In particular, to simplify the node configuration, we propose a reduction in the number of optical amplifiers used for node loss compensation and experimentally verify its feasibility.

S. Camatel

Papers

Narrow Linewidth CW Laser Phase Noise Characterization Methods for Coherent Transmission System Applications

Optical Phase Locking techniques: an overview and a novel method based on Single Side Sub-Carrier modulation

100 Mb/s Ethernet Transmission Over 275 m of Large Core Step Index Polymer Optical Fiber: Results From the POF-ALL European Project

Design, Analysis and Experimental Testing of BPSK Homodyne Receivers Based on Subcarrier Optical Phase-Locked Loop

First demonstration of a C + L band CDC-ROADM with a simple node configuration using multiband switching devices