Optical Signal Processing and Pulse Shaping for Wavelength Multiplexed High Speed Communication Systems

The steady growth of capacity demand in telecommunication networks has sparked the development of various photonic devices for ultrafast optical signal processing functions to meet the requirements of future flexible fiber networks in general and backbone in particular. Although these photonic devices expand the electrical bandwidth operation, they mostly operate at single wavelength and hence remain non-viable solutions for practical implementation in WDMnetworks that are considered as the major technology for high speed communications. Another key challenge of future optical networks is the ability tomerge channels in time and frequency domain in the most efficient way in order to reach the theoretical Nyquist limit of transmission links. A promising technique is the use of sinc-shaped Nyquist pulses that enable multiplexing channels in time domain with no inter-symbol interference (ISI) while exhibiting a rectangular spectrumthat alleviates the need for guard-band. The sinc pulse is indeed the basic building block in most theoretical papers that have estimated overall capacity limits, and intense efforts are being made to generate optical Nyquist pulses beyond the limit of electronics that can directly be used at the physical layer. Within the above context, two approaches, referred to as optical signal processing of WDM networks and generation/detection of Nyquist superchannels, have been studied in this thesis. The first addressed problem is simultaneous signal processing of WDMchannels. We present two principal blocks required for routing and transporting data in WDM networks, both based on dual-pump fiber optical parametric amplifier (FOPA) with (sinusoidally) modulated pumps. We show that this scheme can be designed to operate simultaneously on WDM channels at any desired wavelength range. The former block enables simultaneous wavelength conversion and time compression which is a necessary functionality in connecting dissimilar rate WDM networks. The latter processing block is all-optical 3R regeneration (reamplification, reshaping, retiming) which is crucial for maintaining pulse quality along long-haul WDMlinks. We use theoretical analysis supported by experimental results to demonstrate the efficiency of the proposed technique. The second problem that we investigate is the generation and detection of WDM-Nyquist superchannels. We developed a simple technique based onMach-Zehnder modulators (MZM) to generate a sinc-shaped Nyquist time window by direct synthesis of a rectangular, phase locked frequency comb. We show the produced pulses have exceptional quality as well as high tunability in terms of pulse width and repetition rate. We also further demonstrate a noncoherent method based on the proposed technique to performreal-time demultiplexing of WDM-Nyquist superchannels, simultaneously in time and frequency. The experimental results that are proved by mathematical analysis are employed to demonstrate the effectiveness of the proposed methods

A simple all-optical format transparent time and wavelength demultiplexing technique for WDM & Orthogonal-TDM Nyquist channels

A novel and simple non-coherent method to demultiplex WDM and orthogonal TDM Nyquist signal is presented. Using intensity modulators and filter, demultiplexing from a 3x8x10 = 240 Gb/s signal down to 10 Gb/s is demonstrated

Experimental investigation of pulse generation with one-pump fiber optical parametric amplification

In a recent study, the theory of pulse generation with fiber optical parametric amplification using sinusoidal (clock) intensity modulated pump was revisited [1]. This work showed that the pulses generated through such parametric interaction exhibit a shape which depends on the signal detuning with respect to the pump position (i.e. linear phase mismatch). A near Gaussian shape can only be achieved over a small region of the gain spectrum, close to the maximum gain location. Towards the extremities of the gain spectrum, the generated pulses take a near Sinc shape which can have many potential applications such as for all-optical Nyquist limited transmitters and/or receivers. In this paper we experimentally verify the theory at repetition rates up to 40 GHz. We also discuss the impact of noise, pump saturation and walk-off on the generated pulses

Broadband Uniform Wavelength Conversion and Time Compression of WDM Channels

A scheme based on 2-pump OPA is proposed for uniform wavelength conversion and optimized compression. We show 4.7-fold compression over 32 nm range resulting in Gaussian pulses from sinusoidal modulation and enabling simultaneous compression of WDM channels for granularity adaptation

Wideband All-Optical 3R WDM Regeneration Based on Dual-Pump Parametric Amplifier

Simultaneous all-optical 3R regeneration of WDM channels is demonstrated, based on dual-pump parametric amplification with sinusoidal modulated pumps. We observe receiver sensitivity improvement better than 1.5dB for five WDM channels modulated with 10Gb/s NRZOOK data

Wideband Uniform Generation of Shape-Adjustable Pulses in Two-Pump Fiber Optic Parametric Amplifier

A tunable, stable pulse generation technique based on two-pump fiber optic parametric amplification is theoretically analyzed and experimentally demonstrated to generate uniform near-Gaussian pulses over 32 nm. It is shown that pulse shape can also be tuned and that a specific phase matching case enables Nyquist pulse generation over a wide bandwidth

Wideband generation of pulses in dual-pump optical parametric amplifier: theory and experiment

The generation of pulses in dual-pump fiber optical parametric amplifier is investigated. Theoretically, it is shown that in an analogical manner to pulse generation in single-pump fiber optical parametric amplifiers, the generated pulse shape depends on the linear phase mismatch between the interacting waves. However the dual-pump architecture allows for the bounding of the phase mismatch over a wide bandwidth. This feature permits the generation of uniform pulses over a wide bandwidth, contrary to the single-pump architecture. Using the developed theory, a pulse source with uniform pulses at 5 GHz repetition rate and duty cycle of 0.265 over 40 nm is demonstrated

Bandwidth and repetition rate programmable Nyquist sinc-shaped pulse train source based on intensity modulators and four-wave mixing

We propose and experimentally demonstrate an all-optical Nyquist sinc-shaped pulse train source based on intensity modulation and four-wave mixing. The proposed scheme allows for the tunability of the bandwidth and the full flexibility of the repetition rate in the limit of the electronic bandwidth of the modulators used through the flexible synthesis of rectangular frequency combs. Bandwidth up to 360 GHz at 40 GHz rate and up to 45 frequency lines at 5 GHz rate are demonstrated with 40 GHz modulators. (C) 2014 Optical Society of Americ

Optical Nyquist-pulse generation with a power difference to the ideal sinc-shape sequence of < 1%

Sinc-shaped Nyquist-pulses possess a rectangular spectrum. Thus, a sinc-pulse transmission minimizes the carrier spacing down to the baud rate, and therefore, substantially increases the transmissible data rates. These perspectives have led to a strong research activity in the field of Nyquist pulse transmission. However, all methods of Nyquist pulse generation shown up to now are rather complex, costly and none leads to ideal sinc-shaped Nyquist pulses. Thus, it has not been clear yet if Nyquist-pulse transmission can be incorporated in optical networks in an energy and cost-effective way. Here we present a method for the generation of almost ideal sinc-shaped Nyquist pulses based on a flat and phase-locked frequency comb. The pulses can be generated with conventional modulators without any sophisticated electronics or other costly equipment. In our proof-of-concept experiment we generate sinc-shaped Nyquist-pulse sequences which show a power difference lower than 1% compared to an ideal sequence. Generated sinc pulses have a full width at half maximum (FWHM) duration of 9.8 ps, an out-of-band suppression of more than 27 dB, a signal-to-noise ratio of more than 40 dB and a jitter of 82 fs, equivalent to 0.82% of the FWHM. The pulse width and repetition rate can be changed simply by tuning the comb parameters

Generation of Nyquist sinc pulses using intensity modulators

Optical sinc-shaped Nyquist pulses are produced based on the generation of an ideal frequency comb using cascaded intensity modulators. Nyquist pulses with 9.8-ps temporal width, 82-fs jitter and more than 40 dB SNR are achieved