Tuomo von Lerber

Saturated collision amplifier reach extender for XGPON1 and TDM/DWDM PON

Saturated Collision Amplifier (SCA) is a novel amplification scheme that uses SOA saturation in order to maximize the output power and minimize the ASE noise and the polarization sensitivity. We demonstrate the SCA reach extension in a commercial single-wavelength XGPON1 prototype system where bidirectional optical budget of up to 50 dB is obtained. The traffic performances are compared between the SCA and the conventional SOA extender. The novel extension scheme is demonstrated also for two- and four-wavelength 10 Gbit/s unidirectional downstream configurations with 45 km and 100 km transmission distances with 58-dB maximum total optical budget for each wavelength.

Fiber ringdown-beat pressure sensors

In this paper, we propose and experimentally demonstrate a pressure sensor based on birefringent single mode fiber FP cavity using optical heterodyne. The proof of concept device consists of a light source, a polarizer controller, a modulator, a RF generator, a single mode fiber Fabry-Perot cavity, a strain inspector, an erbium doped fiber amplifier, a filter, a polarizer, an optical spectrum analyzer, and a digital communication analyzer. The dynamic range of the proposed sensor is explored. The results demonstrate the new concept of fiber pressure sensors and the technical feasibility for pressure measurements.

Polarization Independent All-optical Clock Recovery Scheme based on Biréfringent Resonator

We introduce a polarization insensitive scheme for all-optical clock recovery and demonstrate how it works with data signals highly distorted by chromatic dispersion and self-phase modulation. The scheme which is known for its multi-wavelength and multi-data-rate capabilities is based on a birefringent fiber resonator and a polarizer. In this article we show how it can handle data signals which have undergone distortion due to transmission over dispersive and nonlinear fiber-optic propagation paths and which come in with arbitrary polarization orientation. Bit-pattern dependent amplitude fluctuations of the recovered clock signal are equalized by means of a semiconductor optical amplifier operated in saturation. The experimental results which, as a proof-of-concept, are obtained from single-wavelength channel 10 Gbit/s return-to-zero data agree well with numerical simulations.

The influence of bit pattern effects on clock recovery in phase shift keyed fiber-optic transmission systems

Sophisticated modulation formats like phase shift keying (PSK) as discussed for high-speed fiber-optic transmission systems operating at 40 Gbit/s and beyond, cause new challenges for clock recovery. Whereas conventional return-to-zero on-off keyed (RZ-OOK) modulated signals provide proper clock tones which can be used to recover the clock signal, the additional phase modulation (RZ-PSK) changes the spectral composition of the signal and weakens or suppresses the clock tones. This effect is bit pattern dependent as can be seen from a simple example: If all the pulses in an RZ-PSK signal are in phase, the result is equivalent to an ordinary RZ on-off-keying (OOK) signal with a strong carrier and clock tones. If the pulses in a sequence oscillate in phase by &pgr;, the result is equivalent to the well-known carrier-suppressed return-to-zero signal (CS-RZ) where the carrier is suppressed and where clock tones are differently spaced compared to RZ-OOK. In this paper we present results of the simulation of the different cases taking into account realistic bit sequences and analyze the results with special emphasis on the influence the effect has on clock recovery.

Saturated collision amplifier for the extended reach Passive Optical Networks: The upstream challenge

In this paper we discuss about the extended reach 10-Gbit/s Passive Optical Network (XGPON) and the use of a Saturated Collision Amplifier (SCA) for the up- and downstream extension. Especially the upstream amplification is challenging because of the used (i.e. standardized) wavelength and the bursty nature of the traffic. In order to benefit the SCA scheme, the Optical Network Units (ONUs) have to be equipped with low-cost DPSK transmitters. The use of widely tunable direct modulated VCSELs are proposed and discussed.

Q‐Factor Improvement of Phase Noise Degraded DPSK Signals Using Asymmetric Saturated Regeneration

We demonstrate a 6.3 dB improvement in Q‐factor for RZ‐DPSK signals using a shifted filter after a highly saturated SOA working in a contra‐propagating colliding pulse scheme. We show first, both theoretically and by means of simulations, how the phase noise is transformed after demodulation. Then, we demonstrate experimentally, for the first time, that this configuration induces a spectral asymmetry in addition to self phase modulation that if associated with a shifted filter, removes significantly the noise present in both the demodulated marks and spaces. The Asymmetric Saturated Regeneration (ASR) is an enhanced version of the fiber based Mamyshev regenerator.

Roadmap for low-cost optical regeneration

Future transparent networks require optical regeneration. The regeneration process of amplitude-modulated signals consists of three key stages: re-amplification, re-shaping, and re-timing. In this Paper we briefly review various optical clock recovery methods and propose a polarization insensitive low-cost scheme capable of resolving timing information simultaneously for multiple wavelength channels. We also discuss the prospects of low-cost volume production with integrated optics and especially with Si-photonics.