Papers by Stephan Pachnicke
In this article an optical network unit (ONU) has been demonstrated with real-time data traffic b... more In this article an optical network unit (ONU) has been demonstrated with real-time data traffic based on a tunable laser operating without a thermo-electric cooler (TEC) and without an integrated wavelength reference (etalon). Instead a centralized wavelength control system has been deployed, which uses only one shared etalon at the optical line terminal (OLT) to transmit wavelength locking information to all attached ONUs. Different wavelengths can be distinguished in this scheme by different pilot-tones. The control information on wavelength accuracy is provided back to the ONU through an embedded communication channel (ECC). The data rate of the upstream traffic has been set to 1.25 Gb/s (1 GbE). We have shown in a laboratory experiment that the ONU can tune automatically to the desired wavelength and can keep this wavelength within a small tolerance region even when the temperature is changing.
Journal of Lightwave Technology, 2015
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
An electronic feedback gain control for the suppression of transients in EDFA chains is analyzed.... more An electronic feedback gain control for the suppression of transients in EDFA chains is analyzed. It is shown that the optimal parameters for a single amplifier do not lead to optimal results for cascaded EDFAs.
Journal of Optical Networking, 2007
We report our investigations on the impact of transients stemming from channel reconfiguration or... more We report our investigations on the impact of transients stemming from channel reconfiguration or network failure. Erbium-doped fiber amplifier (EDFA) gain dynamics are considered by an average-inversion-level model. The simulation model is also verified by laboratory experiments. In extensive simulations, optimal sets of parameters for an electronic EDFA gain controller have been determined. We show that better results can be obtained if the gain controller is optimized for a chain of EDFAs and not a single amplifier only. Additionally, an efficient simulation methodology to calculate the combined bit error ratio (BER) is presented by coupling simulations of transient phenomena with bit-based simulations incorporating nonlinear fiber effects.
2006 Optical Fiber Communication Conference and the National Fiber Optic Engineers Conference, 2006
The impact of XPM-induced birefringence on 10 Gb/s NRZ intensity modulated transparent optical ne... more The impact of XPM-induced birefringence on 10 Gb/s NRZ intensity modulated transparent optical networks is investigated. The impairments are experimentally measured for different inline dispersion compensation maps and realistic setups with SSMF or mixed fiber.
Optical Fiber Communication Conference, 2010
PolMux increases PMD sensitivity compared to single polarization transmission. We investigate the... more PolMux increases PMD sensitivity compared to single polarization transmission. We investigate the equalization of first and second order PMD in the optical domain and determine the respective remaining penalties induced by DGD, PCD and DEP.
Asia Communications and Photonics Conference 2013, 2013
ABSTRACT We present an experimental study on downstream broadcast overlay in WDM-PON systems usin... more ABSTRACT We present an experimental study on downstream broadcast overlay in WDM-PON systems using a low-cost reflective semiconductor optical amplifier (RSOA) as broadband signal source. Reach and achievable bitrate are compared for S- and C-Band overlay.
Optical Fiber Communication Conference, 2015
Optical Transmission Systems and Equipment for WDM Networking II, 2003
In this paper cross-phase modulation (XPM) and its impact on multispan NRZ-modulated wavelength d... more In this paper cross-phase modulation (XPM) and its impact on multispan NRZ-modulated wavelength division multiplexing (WDM) systems is examined. An analytical model is presented to assess the signal degradation. The impairments due to XPM are related to a Q-factor. The presented formulas are examined for different dispersion compensation schemes and also mixed-fiber systems. The analytical models are verified by system
Journal of Lightwave Technology, 2014
ABSTRACT This paper reports an uncooled transmitter system using a digital super-mode (DS) distri... more ABSTRACT This paper reports an uncooled transmitter system using a digital super-mode (DS) distributed Bragg reflector (DBR) tunable laser, which is able to act as an athermal, wavelength agnostic transmitter suitable for wavelength division multiplexed (WDM) passive optical network (PON) applications. An open-loop laser current control algorithm is designed to compensate autonomously for wavelength drift, thus allowing constant operating wavelength to be achieved regardless of ambient temperature. An improved wavelength accuracy of ±3 GHz is achieved when using low bandwidth feedback from the central office using information from a centralized shared wavelength locker. The entire laser start-up, channel selection and subsequent wavelength control is autonomous and has been implemented on micro-controllers and field programmable gate arrays. We demonstrate a three channel WDM-PON system comprising an uncooled packaged DS-DBR laser in the presence of two neighboring interfering channels. Error free transmission over 40 km single mode fiber of 10 Gb/s externally modulated NRZ data, is achieved for each of 48 C-band channels on the 100 GHz ITU grid. Successful athermal operation is demonstrated by sweeping the ambient temperature of the laser from 15 to 70 °C with a maximum wavelength deviation for any channel of no more than 0.1 nm.
CLEO: 2014, 2014
ABSTRACT We describe the performance of an optimized high-temperature DS-DBR laser used as an unc... more ABSTRACT We describe the performance of an optimized high-temperature DS-DBR laser used as an uncooled WDM source. Constant wavelength output with less than 6GHz error without mode-hopping is shown for C-band channels from 70-90 °C.
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT We present a study on wavelength stability requirements for next generation passive opti... more ABSTRACT We present a study on wavelength stability requirements for next generation passive optical network (PON) access systems in the light of induced timing jitter. Based on these findings different realization options of wavelength control methods for use in wavelength tunable PON systems are investigated.
Journal of Lightwave Technology, 2015
Journal of Optical Communications and Networking, 2014
ABSTRACT In this paper, a wavelength-division-multiplexing passive optical network (WDM-PON) syst... more ABSTRACT In this paper, a wavelength-division-multiplexing passive optical network (WDM-PON) system using small form-factor pluggable plus (SFP+) packaged full C-band tunable transceivers is demonstrated for the first time to our knowledge. Within the transceivers, a novel digital-supermode distributed Bragg reflector (DS-DBR) laser with a monolithically integrated Mach–Zehnder modulator is employed as the transmitter. A generic current control algorithm is used to drive the DS-DBR laser, which employs a laser current training sequence ensuring successful operation without the need for individual laser characterization. A pilot-tone-based feedback control loop is implemented using embedded hardware, which is able to lock the output wavelengths from three identical optical network units with less than ± 3 GHz deviation from their assigned channels. Error-free transmission is achieved at a 10 GbE data rate. With the feedback control loop running continuously, the system shows a sensitivity of − 23 dBm for a bit error rate of 10 − 12 .
Optical Fiber Communication Conference, 2014
ABSTRACT We demonstrate automatic operation of a cooler-less tunable-laser based WDM-PON system. ... more ABSTRACT We demonstrate automatic operation of a cooler-less tunable-laser based WDM-PON system. Using a pilot-tone based overhead channel and centralized wavelength locking scheme, 1 Gb/s and 10 Gb/s data transmission is demonstrated in a multi-user set-up.
Optical Fiber Communication Conference, 2014
ABSTRACT
Optical Fiber Communication Conference, 2014
The use of single-sideband subcarrier modulation (SCM) with Nyquist (N) pulse shaping for cost-ef... more The use of single-sideband subcarrier modulation (SCM) with Nyquist (N) pulse shaping for cost-effective spectrally-efficient wavelength division multiplexed transmission with direct detection is described. Transmission of digitally pre-compensated 7 × 11 GHz-spaced QPSK SCM channels at 14 Gb/s per channel is experimentally demonstrated over distances of up to 800 km of uncompensated standard single-mode fiber (SSMF) (13440 ps/nm chromatic dispersion).
Optical Fiber Technology, 2009
The sensitivity of optical orthogonal-frequency division multiplexing (OFDM) transmission to the ... more The sensitivity of optical orthogonal-frequency division multiplexing (OFDM) transmission to the finite resolutions of the digital-to-analog (DAC) and analog-to-digital converters (ADC) has been analyzed using numerical simulations. We show that for back-to-back configuration the requirements regarding the number of quantization bits for the DACs are similar to the ones of the ADCs. After transmission over metro and long-haul distances a higher resolution of the DAC/ADC is required compared to back-to-back configuration. We show that after transmission it is sufficient to enhance either the ADC resolution or the DAC resolution by 1 bit.
Journal of Lightwave Technology, 2000
Constraint-based routing (CBR) requires a fast and accurate assessment of the different physical ... more Constraint-based routing (CBR) requires a fast and accurate assessment of the different physical degradation effects in optical communications systems. This paper deals with fast analytical approximation formulas describing the induced system penalty due to the dominant nonlinear effects in 10-Gb/s nonreturn to zero (NRZ) transmission systems. This paper concentrates on the multichannel effects of cross-phase modulation (XPM) and four-wave mixing
Journal of Lightwave Technology, 2000
Dynamic optical communication systems require fast assessment of the signal quality of the desire... more Dynamic optical communication systems require fast assessment of the signal quality of the desired path through the network. This paper presents an analytical approach for describing the Q-factor due to linear (group velocity dispersion, noise, and polarization-mode dispersion) as well as the dominant nonlinear effects in 10-Gb/s nonreturn-to-zero ON-OFF keying transmission systems
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Papers by Stephan Pachnicke