Rasmus Kjær

Slow light in a semiconductor waveguide at gigahertz frequencies

We experimentally demonstrate slow-down of light by a factor of three in a 100 microm long semiconductor waveguide at room temperature and at a record-high frequency of 16.7 GHz. It is shown that the group velocity can be controlled all-optically as well as through an applied bias voltage. A semi-analytical model based on the effect of coherent population oscillations and taking into account propagation effects is derived and is shown to well account for the experimental results. It is shown that the carrier lifetime limits the maximum achievable delay. Based on the general model we analyze fundamental limitations in the application of light slowdown due to coherent population oscillations.

85 km Long Reach PON System Using a Reflective SOA-EA Modulator and Distributed Raman Fiber Amplification

We report on a bidirectional 85 km long reach PON system supported by distributed fiber Raman amplification with a record 7.5 Gb/s remote carrier modulated upstream signal by employing a reflective SOA-EA monolithically integrated circuit

Bi-directional 120 km Long-reach PON Link Based on Distributed Raman Amplification

We propose and demonstrate a bidirectional PON link with 120 km reach and symmetric up and down stream data rate of 10 Gbit/s. Lossless transmission was achieved with >40 dB of received OSNR

10 Gb/s bidirectional single fibre long reach PON link with distributed Raman amplification

We report operation of a single fibre bidirectional 80 km long reach PON link with symmetric up- and-downstream data rate of 10 Gb/s supported by distributed Raman fibre amplification only.

Steep and adjustable transfer functions of monolithic SOA-EA 2R regenerators

Measurements and numerical modeling of a reamplification and reshaping (2R) regenerator demonstrate a steep power transfer function with adjustable threshold. The threshold can be adjusted more than 6 dB by simple control of the reverse bias voltage of the absorber section. The device consists of a semiconductor waveguide with alternating amplifier and absorber sections using quantum-well active material. The steep nonlinearity of the transfer function is achieved by concatenating several sections. We identify the saturation properties of the absorbing media, as dictated by the band-filling and field screening, as important for the observed transfer functions. The relation of the saturation powers of the gain and absorption sections is important for design optimization.

Reflective SOA re-modulated 20 Gbit/s RZ-DQPSK over distributed Raman amplified 80 km long reach PON link

An 80 km bidirectional Raman amplified long reach PON link has been demonstrated. A 20 Gbit/s RZ-DQPSK signal was transmitted downstream, ASK-remodulated at 1.25 Gbit/s by an RSOA and transmitted upstream in the same fiber. Both signals were detected error free without use of EDFAs.

All-optical equalization of power transients on four 40 Gbit/s WDM channels using a fiber-based device

Simultaneous transient suppression of four transient-impaired 40 Gbit/s RZ-ASK WDM channels is demonstrated. Sensitivity improvements are in excess of 5 dB and transmission penalties are significantly reduced.

Raman-assisted transmission of 16×10 Gbit/s over 240 km using post-compensation only

We demonstrate transmission of 16 WDM channels at 10 Gbit/s with 50 GHz channel spacing over 3 times 80 km NZDSF, with small OSNR penalty, using only a single Raman-pumped dispersion compensating module positioned before the receiver.

Slow Light in Semiconductor Waveguides

We describe recent experiments demonstrating slow-down of light in a semiconductor waveguide at gigahertz frequencies. The results are explained by a simple model, which is used to analyze the potential and limitations of the technique.

Hybrid Erbium/Raman Fiber Amplifier with High Dynamic Range and Low Gain Ripple in Entire C-Band

A standard dual-stage EDFA is combined with a dispersion-compensating Raman amplifier to obtain flat C-band gain in a high-gain range from 20 dB to 33 dB. The amplifier may find use in long-span repeater links.