Huug de Waardt

Error-free all-optical wavelength conversion at 160 gb/s using a semiconductor optical amplifier and an optical bandpass filter

Error-free and pattern-independent wavelength conversion at 160 Gb/s is demonstrated. The wavelength converter utilizes a semiconductor optical amplifier (SOA) with a recovery time greater than 90 ps and an optical bandpass filter (OBF) placed at the amplifier output. This paper shows that an OBF with a central wavelength that is blue shifted compared to the central wavelength of the converted signal shortens the recovery time of the wavelength converter to 3 ps. The wavelength converter is constructed by using commercially available fiber-pigtailed components. It has a simple configuration and allows photonic integration.

High Capacity Mode-Division Multiplexed Optical Transmission in a Novel 37-cell Hollow-Core Photonic Bandgap Fiber

We present the first demonstration of combined wavelength-division multiplexed (WDM) and mode-division multiplexed (MDM) optical transmission in a hollow-core photonic bandgap fiber (HC-PBGF). For this purpose a novel low loss, broadband 310 m long HC-PBGF with a 37 cell (37c) core geometry is used. The modal properties of the HC-PBGF are characterized in detail, showing an absence of surface modes and low modal crosstalk, which enable WDM and MDM transmission with record high capacity (73.7 Tb/s) for a HC-PBGF. Several modulation formats have been tested, showing very good and stable performance. The transmission properties are assessed by looking into both single-mode transmission and MDM transmission, showing good agreement with the modal characterization of the 37c HC-PGBF.

On the Mitigation of Optical Filtering Penalties Originating From ROADM Cascade

Wavelength selective switches (WSSs) that are integrated in reconfigurable optical add-drop multiplexers (ROADMs) induce penalties on the optical signal due to tight optical filtering, which increases as several ROADMs are cascaded in a meshed network. In this letter, we propose and analyze possible configurations for the mitigation of these penalties in optical domain using optical wave shaper (WS). Including one WS in every ROADM node allows transmission of 28 and 32 GBd signals, which are QPSK, 8-QAM, or 16-QAM modulated, through a cascade of 32 and 14 WSS filters, respectively. With an average bandwidth of 33 GHz per WSS, an optical signal to noise ratio penalty below 1 dB at BER=1×10-3 is observed.

16/spl times/40 gb/s over 800 km of SSMF using mid-link spectral inversion

We demonstrate the feasibility of a cost-effective 640 Gb/s (16/spl times/40 Gb/s) wavelength-division-multiplexed (WDM) transmission system over 800 km of conventional standard single-mode fiber (SSMF) without using in-line dispersion management. Instead for chromatic-dispersion compensation, a Magnesium-oxide-doped periodically poled lithium niobate (MgO : PPLN)-based polarization-diverse subsystem is used to phase conjugate all 16 channels. The transmission line uses all erbium-doped fiber amplifiers and has an amplifier spacing of 100 km. All channels launched were copolarized. To the best of our knowledge, this is the first WDM transmission experiment with a channel data rate of 40 Gb/s using a PPLN as chromatic-dispersion compensator.

Ultralong haul 1.28-Tb/s PM-16QAM WDM transmission employing hybrid amplification

In order to cope with the foreseeable capacity crunch next-generation optical transmission systems aim to utilize higher order quadrature amplitude modulation formats to achieve spectral efficiency (SE) higher than the current commercial systems. In particular, transmission rates as high as 1 Tb/s are envisioned, employing superchannel configuration achieved by closer than standard 50 GHz placement of Nyquist filtered wavelength-division multiplexed (WDM) channels. Moreover, increase in symbol rate of each subcarrier in a superchannel is desired to reduce the number of components per Tb/s and, consequently, overall cost. In this regard, we addressed a series of challenges namely intersymbolinterference (ISI) induced by low-pass filtering of digital-to-analog converter (DAC), intrasuperchannel crosstalk penalties, and selected suitable forward error correction (FEC) code considering limitations of electronic components. Digital preemphasis is employed to mitigate DAC induced ISI, a subcarrier spacing of 1.2 × symbol rate is chosen to limit crosstalk penalties below 0.5 dB in Q2 and a FEC overhead of 23% is established limiting transponder count to four, achieving 1 Tb/s net data rate. The superchannel is assigned a 200-GHz optical spectrum to achieve a SE of 5.0 b/s/Hz, and WDM transmission performance is evaluated over three different kinds of fibers: standard single-mode fiber (SSMF), large area pure silica core fiber (LAPSCF), and large effective area fiber (LEAF), having span lengths of 95/121, 82/164, and 81 km, respectively. The maximum reach of 1-Tb/s superchannel with 8 × 100-Gb/s WDM channels at pre-FEC threshold of 3.37 × 10-2 was found to be 1110, 1921, and 789 km for SSMF, LAPSCF, and LEAF, respectively. Further improvement in transmission performance is achieved by employing hybrid EDFA-Raman amplification, and achievable distance was extended to 2054, 2952, and 1341 km for SSMF, LAPSCF, and LEAF, respectively, at pre-FEC threshold. Mitigation of a nonlinear phase noise employing single-channel digital back propagation resulted in extension of maximum reach up to 2262, 3349, and 1530 km for SSMF, LAPSCF, and LEAF, respectively.

Demonstration of a Photonic Integrated Mode Coupler With MDM and WDM Transmission

In this letter, 3.072-Tb/s (six spatial and polarization modes × 4 wavelength-division multiplexing (WDM) ×128-Gb/s 16QAM) transmission over 30 km of few-mode fiber (FMF) is demonstrated employing a photonic integrated mode coupler based on silicon-on-insulator (SoI) technology. A 2-D top coupling solution with five small vertical grating couplers is proposed for coupling between an SoI chip and an FMF, guiding LP01 and LP11 modes. Push-pull and center launch configurations for exciting LP11 and LP01 modes, respectively, through mode-profile matching are analyzed and implemented on the SoI chip.

Employing Prism-Based Three-Spot Mode Couplers for High Capacity MDM/WDM Transmission

Based on a three-surface prism, a free space design of the three-spot mode coupler, supporting LP01 and LP11 modes, is introduced in this letter. We demonstrate 7.68 Tbit/s transmission of three mode division multiplexing (MDM) × 8 wavelength division multiplexing (WDM) × 320-Gb/s dual-polarization (DP)-32QAM over a 120 km differential-group-delay (DGD)-compensated few-mode fiber (FMF) by employing the proposed spot couplers.

On the filter narrowing issues in elastic optical networks

This paper describes the problematic filter narrowing effect in the context of next-generation elastic optical networks. First, three possible scenarios are introduced: the transition from an actual fixed-grid to a flexi-grid network, the generic full flexi-grid network, and a proposal for a filterless optical network. Next, we investigate different transmission techniques and evaluate the penalty introduced by the filtering effect when considering Nyquist wavelength division multiplexing, single side-band direct-detection orthogonal frequency division multiplexing, and symbol-rate variable dual polarization quadrature amplitude modulation. Also, different approaches to compensate for the filter narrowing effect are discussed. Results show that the specific needs per each scenario can be fulfilled by the aforementioned technologies and techniques or a combination of them, when balancing performance, network reach, and cost.

Advanced Differential Modulation Formats for Optical Access Networks

The use of incoherent multilevel modulation formats with high spectral efficiency (more than two bits per symbol) has been proposed in order to enable the next generation of very high-speed Time-Division Multiplexing Passive Optical Networks (TDM-PONs). Incoherent multilevel modulation is attractive for access applications since multilevel formats allow the scaling of the bit rate with electronic and photonic components operating at a fraction of the bit rate. On the other hand, incoherent detection reduces the requirement for complicated Digital Signal Processing (DSP) and crucially an additional local oscillator, compared to coherent receivers. The modulation formats examined are Differential 8 Phase-Shift Keying (D8PSK) and three versions of incoherent 16 Quadrature Amplitude Modulation (QAM), specifically Star 16QAM, coded square 16QAM and 16QAM with pre-integration. Generation and detection of these formats is discussed, as well as the implementation challenges associated with such advanced modulation formats. The performance of these modulation formats was evaluated through extensive simulation and experimental work. Results indicate that incoherent modulation can fulfill important requirements of networks operators, namely increased bit rate and increased splitting ratio, and provide a cost-effective solution for Next-Generation Optical Access Networks.

Comparison of Maximum Likelihood Sequence Estimation equalizer performance with OOK and DPSK at 10.7 Gb/s

We experimentally compare MLSE equalization with OOK and DPSK in the presence of chromatic- and polarization-mode dispersion. We show that the 3-dB OSNR advantage of DPSK is lost in the presence of chromatic dispersion but maintained with polarization-mode dispersion.