Analysis of delay-and-multiply optical FSK receivers with line-coding and non-flat laser FM response

Forestieri, E.; Prati, G.

doi:10.1109/49.372413

Cited by 12 publications

(2 citation statements)

References 32 publications

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“…The former effect is dominant only at low frequencies (<~10 MHz), whereas the latter exhibits a flat response from DC to several GHz with a resonance like behavior at much higher frequencies. The overall FM response of the laser diode at low frequencies then becomes nonuniform because the vector addition of the thermal FM and the carrier FM produces a 'dip' at around 1 MHz [13], [14]. Different approaches have been reported to combat this problem such as pre-equalization of the laser driving signal [15], the use of multi-electrode laser diodes (LDs) [16], and the use of a preamplifier with a compensation network to enhance the signal at the laser FM response dip [17].…”

Section: Introductionmentioning

confidence: 99%

Directly modulated laser transmitter driven by DC-balanced line-coded signals

Kim

2010

2010 IEEE International Conference on Communication Systems

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Directly modulated laser (DML) based optical transmitters provide cost-effectiveness, small footprint, high output power, and high reliability. However, the signal quality of the DML output is poorer than that of external modulator-based counterpart, mainly because of the frequency chirp accompanied by current modulation of DMLs. Especially, the large current modulation to achieve high extinction ratio of the output signals induces severe chirp and waveform distortion that the transmission distance is significantly limited in high data-rate systems. This can be overcome with frequency modulation of DMLs. By making good use of the frequency modulation of DMLs, not only can we reduce the driving voltage but we also substantially reduce the deleterious effects of chirped modulation. However, frequency modulation (FM)-based DML transmitters suffer from the non-uniform FM response of the laser at around 100 kHz to 10 MHz. It gives rise to severe pattern-dependent performance degradation to directly modulated baseband signals. In this paper, we investigate through experiment the use of line coding to deplete the low-frequency spectral contents of the signals and thus to alleviate the degradation. We measure the performance improvement of various line codes, including 8B/10B, 5B/6B, 7B/8B, 9B/10B, and 64B/66B, for continuousphase frequency-shift keying (CPFSK)/amplitude-shift keying (ASK) signals generated by a DML and a delay interferometer. Experimental demonstrations are performed with a long pseudorandom bit sequence length of 2 20 -1 and the bandwidth expansion by the line coding is taken into consideration. We also propose and demonstrate DML-based transmitters driven by highly band-limited electrical signals to alleviate the modulation bandwidth limitation. By using duobinary coding together with DC-balanced line coding, we generate 10-Gbps signals using a DML driven by 3.5-GHz-bandwdith signals and transmit them over 20-km of standard single-mode fiber without any dispersion compensation.

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Section: Introductionmentioning

confidence: 99%

Directly modulated laser transmitter driven by DC-balanced line-coded signals

Kim

2010

2010 IEEE International Conference on Communication Systems

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“…At the TX side, for instance, direct current modulation of DFB lasers, leveraging the frequency chirp, is pointed out in this thesis as a cost-effective optical modulation strategy for access networks, with remarkable simplicity and power efficiency. Yet, a major challenge arises from the non-ideal FM response of DFBs under injection current modulation [For95]. Moreover, electronic components of the TX and the RX such as amplifiers, electrical filters, RF mixers, ADCs/DACs, etc., might also exhibit non-flat frequency response in the pass-band.…”

Section: Non-flat Electro-optical Frequency Responsementioning

confidence: 99%

Transmission impairments mitigation in next generation coherent optical access networks

Tabares Giraldo

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Worldwide, the coherent technologies have revolutionized the optical communication systems, significantly increasing the capacity of the fiber channel owing to transmission of advanced modulation formats and effective mitigation of propagation impairments. However, the actual commercial solutions for long-haul core/backbone networks are still complex and costly, and therefore hardly feasible for deployment in optical access networks. In particular, the main limitations arise from the customer premises equipment whose cost, footprint and power consumption may be kept down. Thus, the optimal solutions for next generation coherent optical access are required to achieve high performance but at lower complexity and cost, since in the access scenario the cost-effectiveness takes more relevance over achieving the best system performance. The research described in this thesis primarily aims at the development of the customer equipment “namely the coherent transceiver” for a passive optical access network that implements the novel wavelength-to-the-user concept by serving hundreds of users (e.g., 256 users) with dedicated wavelengths allocated in ultra-narrow optical grid. The proposed access network features complexity-reduced coherent technologies by leveraging photonic integration, commercial low-cost lasers and optics, and consumer electronics. To this end, the thesis investigates on the main transmission impairments that affect signal integrity from source to destination in the access network, and proposes novel and enhanced mitigation strategies by either low-complexity digital signal processing or analog hardware design. The covered topics spread over both the optical transmitter and the coherent receiver subsystems. Simplified optical modulation is addressed by direct phase modulation of semiconductor lasers profiting from the laser chirp. Digital pre-equalization of non-ideal frequency response from electronic/photonic devices “such as lasers, amplifiers and data converters” is investigated, focusing on the tolerance to quantization noise from digital-to-analog converters with limited resolution. Hardware-efficient strategies for optical carrier recovery based on differential phase detection are explored in two scenarios: homodyne receivers aided by digital signal processing, or fully analog heterodyne receivers. Finally, to deal with the critical polarization matching in coherent systems, simplified architectures for polarization-independent coherent receivers using low-cost optics and simpler receiver front-end are investigated. A nivel mundial, las tecnologías coherentes han revolucionado los sistemas de comunicaciones ópticas, aumentando significativamente la capacidad del canal de fibra gracias a la transmisión de formatos de modulación avanzados y a la mitigación efectiva de las degradaciones en la propagación. Sin embargo, las soluciones comerciales actuales para redes troncales de largo alcance siguen siendo complejas y costosas y, por lo tanto, difícilmente viables para su implementación en redes ópticas de acceso. En particular, las principales limitaciones surgen del equipo de usuario cuyo coste, tamaño y consumo de energía deben mantenerse bajos. Por lo tanto, las soluciones óptimas para las redes ópticas de acceso coherentes de nueva generación deben lograr un alto rendimiento pero con menor complejidad y coste, ya que en el escenario de acceso la relación coste-eficiencia toma más relevancia que lograr el mejor rendimiento del sistema. La investigación descrita en esta tesis se enfoca principalmente en el desarrollo del equipo de usuario, es decir, el transceptor coherente¿, para una red óptica pasiva de acceso que implementa el nuevo concepto de longitud de onda al usuario, al servir a cientos de usuarios (e.g., 256 usuarios) con longitudes de onda dedicadas y asignadas en una rejilla óptica ultra estrecha. La red de acceso propuesta implementa tecnologías coherentes de complejidad reducida al aprovechar la integración fotónica, láseres y dispositivos ópticos comerciales y de bajo coste, y electrónica de consumo. Con tal fin, la tesis investiga las principales degradaciones en la transmisión que afectan la integridad de la señal desde la fuente hasta el destino en la red de acceso, y propone nuevas y mejoradas estrategias de mitigación usando tanto procesamiento digital de señales de baja complejidad como diseño de hardware analógico. Los temas tratados abarcan desde el transmisor óptico hasta los subsistemas del receptor coherente. La modulación óptica simplificada se aborda mediante modulación directa de fase de láseres de semiconductor, aprovechando el chirp del láser. Se investiga la pre-ecualización digital de la respuesta frecuencial no ideal de dispositivos electrónicos/fotónicos tales como láseres, amplificadores y conversores de datos, centrándose en la tolerancia al ruido de cuantificación de los conversores digital-analógico con resolución limitada. Las estrategias para la recuperación de la portadora óptica basadas en la detección diferencial de fase y eficientes en hardware, se exploran en dos escenarios: receptores homodinos asistidos por procesamiento digital de señales, o receptores heterodinos completamente analógicos. Finalmente, para hacer frente al crítico ajuste de la polarización en sistemas coherentes, se investigan arquitecturas simplificadas para receptores coherentes independientes de la polarización utilizando óptica de bajo coste y un front-end óptico del receptor más simple.

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PM/AM and AM/PM Conversions in Linear Optical Fibers

Forestieri

1999

Optical Networking

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Analysis of delay-and-multiply optical FSK receivers with line-coding and non-flat laser FM response

Cited by 12 publications

References 32 publications

Directly modulated laser transmitter driven by DC-balanced line-coded signals

Directly modulated laser transmitter driven by DC-balanced line-coded signals

Transmission impairments mitigation in next generation coherent optical access networks

PM/AM and AM/PM Conversions in Linear Optical Fibers

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