Markus Meissner

NOLM-based RZ-DPSK signal regeneration

We present a nonlinear optical loop mirror (NOLM)-based 2R-regenerator setup, which is capable of regenerating signals modulated in phase-sensitive modulation formats. In a conventional NOLM, fluctuations of the signal amplitude are converted into phase fluctuations. Therefore, it is not suitable for regeneration of signals, modulated in formats such as differential phase-shift keying (DPSK) or duobinary. In this letter, we present a modified NOLM setup for 2R-regeneration taking return-to-zero DPSK as an example.

12 dB of noise reduction by a NOLM-based 2-R regenerator

We experimentally demonstrate all-optical all-passive signal regeneration by reducing the noise imposed on the signal by optical amplification by 12.03/spl plusmn/0.13 dB with an asymmetric nonlinear optical loop mirror (NOLM). This signal-to-noise ratio (SNR) enhancement is due to the Kerr nonlinearity which has a timescale below a few femtoseconds, thus, the SNR enhancement by the NOLM is applicable to high bit rates such as 160 Gb/s.

3.9-dB OSNR gain by an NOLM-based 2-R regenerator

We experimentally demonstrate bit-error-rate (BER) improvement of more than nine decades by an asymmetric nonlinear optical loop mirror (NOLM). This can be related to an optical signal-to-noise ratio (OSNR) gain of up to 3.9 dB with respect to the NOLM input OSNR at a bit rate of 40 GB/s. The principle of operation of NOLM-based 2-R regeneration with respect to BER improvement is investigated and it is experimentally shown that BER improvement cannot be detected directly at the regenerators output.

All-fibre source of amplitude squeezed light pulses

An all-fibre source of amplitude squeezed solitons utilizing the self-phase modulation in an asymmetric Sagnac interferometer is experimentally demonstrated. The asymmetry of the interferometer is passively controlled by an integrated fibre coupler, allowing for the optimization of the noise reduction. We have carefully studied the dependence of the amplitude noise on the asymmetry and the power launched into the Sagnac interferometer. Qualitatively, we find good agreement between the experimental results, a semi-classical theory and earlier numerical calculations (Schmitt et al 1998 Phys. Rev .L ett. 81 2446). The stability and flexibility of this all-fibre source makes it particularly well suited to applications in quantum information science.

Innovative optical components and their impact on future optical transmission systems

Optical transmission systems made impressive progress in the field of system capacity, reach and flexibility. Beside all improvements achieved so far, signal distortion on the one hand side and noise accumulation on the other hand side are the limitations of optical transmission system performance. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Our paper reviews signal regeneration techniques focusing on fiber nonlinearity based setups both in interferometric and non interferometric architecture. We analyze the impact of regenerator design parameters as fiber nonlinear parameters, regenerator input power and characteristics of filters on signal improvement and demonstrate e.g. the increase of system reach. In order to address the upcoming techniques of advanced modulation formats we introduce a fiber based regenerator scheme that shows attractive potential especially for phase modulated signals. Combining these new optical formats with regenerative methods is attractive for high performance systems. For the differential phase shift keying (DPSK) modulation format we investigate the potential of a cross phase modulation based type of regenerator in more detail. The availability of suitable regenerator components, especially highly nonlinear fibers is one of the challenges. Especially the new fiber types known as photonic crystal fibers can act as bases for new structures and thus will open the door for ultra high performance optical transmission systems.

All-optical DPSK-signal-regeneration based on a NOLM-setup

We present a novel concept for all-optical DPSK signal regeneration based on a directionally attenuated non linear loop mirror (DA-NOLM).

Chirp-Free Transmission through a NOLM Based Optical Regenerator

We experimentally show that a strongly asymmetric nonlinear optical loop mirror (NOLM) based 2-R regenerator does not degrade the pulse quality in a fiber optic transmission line. The signal at the NOLM output port shows only negligible chirp if a fundamental soliton propagates in the strong arm of the NOLM. This behavior is measured for splitting ratios of 91:09 and 85:15. The NOLM does not insert penalties regarding the pulse shape and is therefore suitable for inline regeneration of optical transmission lines.

BER improvement using a 2-R regenerator based on an asymmetric nonlinear optical loop mirror

BER improvement of 15 decades is observed using an asymmetric NOLM at a bitrate of 40Gbit/s and an input OSNR of 28.7dB. The BER improvement can be converted into 3.9dB of OSNR gain. Both were achieved by optimizing NOLM input power and splitting ratio. This allows for longer spans and thus reduces the over all amount of amplifiers or allows for an increased system reach.

Optical signal regeneration at different modulation formats

Optical transmission systems made impressive progress in the field of system capacity, reach and flexibility. Beside all improvements achieved so far, signal distortion on the one hand side and noise accumulation on the other hand side are the limitations of optical transmission systems. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Furthermore the upcoming techniques of advanced modulation formats build a basis for further improvement of transmission quality that ends up with even higher reach, higher robustness against transmission impairments, lower signal to noise requirements etc. In this talk the current status of research in the field of optical signal regenerators suitable for signal regeneration for different modulation formats will be reviewed and presented, where we restrict our analysis to 2R regenerators. The focus will be put on regenerators taking advantage of non linear optical effects in order to improve signal quality. The main challenge is the treatment of phase modulated signals within regenerators. Especially the differential phase shift keying (DPSK) modulation format or the duobinary modulation format are attractive candidates for such kind of regenerators for further improvement of DPSK based transmission systems. The paper will go through several regenerative concepts like non linear optical loop mirror (NOLM) based and cross phase modulation based regenerators in order to figure out their potential for advanced modulation format based systems.