Cm Chigo Okonkwo

47.4 Gb/s Transmission Over 100 m Graded-Index Plastic Optical Fiber Based on Rate-Adaptive Discrete Multitone Modulation

We experimentally demonstrate a bit-rate of 47.4 Gb/s over 100 m of perfluorinated multimode graded-index plastic optical fiber (GI-POF) by exploiting discrete multitone (DMT) modulation with rate-adaptive bit-loading. The maximum achieved aggregate bit rate is 51.8 Gb/s including DMT transmission overhead (cyclic prefix and preambles) and the standard of 7% of forward-error-correction (FEC) overhead. This is achieved over an intensity-modulated direct-detection (IM-DD) link using a directly-modulated DFB laser (1300-nm) and a multimode fiber-coupled photodetector with a large diameter of 25-¿m. The bandwidth requirement is only 12 GHz due to the use of spectral-efficient modulation formats of up to 64-QAM.

Recent Results From the EU POF-PLUS Project: Multi-Gigabit Transmission Over 1 mm Core Diameter Plastic Optical Fibers

Recent activity to achieve multi-gigabit transmission over 1 mm core diameter graded-index and step-index plastic optical fibers for distances up to 50 meters is reported in this paper. By employing a simple intensity-modulated direct-detection system with pulse amplitude or digital multi-tone modulation techniques, low-cost transceivers and easy to install large-core POFs, it is demonstrated that multi-gigabit transmission up to 10 Gbit/s over 1-mm core diameter POF infrastructure is feasible. The results presented in this paper were obtained in the EU FP7 POF-PLUS project, which focused on applications in different scenarios, such as in next-generation in-building residential networks and in datacom applications.

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.

Compact spatial multiplexers for mode division multiplexing

Spatial multiplexer (SMUX) for mode division multiplexing (MDM) has evolved from mode-selective excitation, multiple-spot and photonic-lantern based solutions in order to minimize both mode-dependent loss (MDL) and coupler insertion loss (CIL). This paper discusses the implementation of all the three solutions by compact components in a small footprint. Moreover, the compact SMUX can be manufactured in mass production and packaged to assure high reliability. First, push-pull scheme and center launch based SMUXes are demonstrated on two mostly-popular photonic integration platforms: Silicon-on-insulator (SOI) and Indium Phosphide (InP) for selectively exciting LP01 and LP11 modes. 2-dimensional (2D) top-coupling by using vertical emitters is explored to provide a coupling interface between a few-mode fiber (FMF) and the photonic integrated SMUX. SOI-based grating couplers and InP-based 45° vertical mirrors are proposed and researched as vertical emitters in each platform. Second, a 3-spot SMUX is realized on an InP-based circuit through employing 45° vertical mirrors. Third, as a newly-emerging photonic integration platform, laser-inscribed 3D waveguide (3DW) technology is applied for a fully-packaged dual-channel 6-mode SMUX including two 6-core photonic lantern structures as mode multiplexer and demultiplexer, respectively.

Cost optimization of optical in-building networks

We compare the CapEx and OpEx of in-building networks for fibre and Cat-5E solutions. For residential homes, our analysis shows that total network costs during economic lifetime are lowest for a point-to-point duplex POF topology.

MIMO equalization with adaptive step size for few-mode fiber transmission systems

Optical multiple-input multiple-output (MIMO) transmission systems generally employ minimum mean squared error time or frequency domain equalizers. Using an experimental 3-mode dual polarization coherent transmission setup, we show that the convergence time of the MMSE time domain equalizer (TDE) and frequency domain equalizer (FDE) can be reduced by approximately 50% and 30%, respectively. The criterion used to estimate the system convergence time is the time it takes for the MIMO equalizer to reach an average output error which is within a margin of 5% of the average output error after 50,000 symbols. The convergence reduction difference between the TDE and FDE is attributed to the limited maximum step size for stable convergence of the frequency domain equalizer. The adaptive step size requires a small overhead in the form of a lookup table. It is highlighted that the convergence time reduction is achieved without sacrificing optical signal-to-noise ratio performance.

Low-Differential-Mode-Group-Delay 9-LP-Mode Fiber

We report the fabrication of low-differential-mode-group-delay 9-LP-mode fibers using a standard bend-insensitive 50μm-diameter-core multimode process. Such 9-LP-mode fibers exhibit DMGDs <; 155ps/km at 1550nm.

Beyond 1 Gbit/s Transmission Over 1 mm Diameter Plastic Optical Fiber Employing DMT for In-Home Communication Systems

Multi-Gbit/s transmission over 1 mm diameter graded index plastic optical fiber (GI-POF) is reported. Transmission rates between 5.3 and 7.6 Gbit/s are achieved for fiber lengths between 10 and 50 m using discrete multi-tone modulation (DMT) in an intensity modulated direct detection system using directly modulated eye-safe VCSEL and silicon photodiode (PD). The used system bandwidth is only 1.42 GHz resulting in a spectral efficiency of bits/s/Hz. All employed components represent a low-cost, off-the-shelf cost-effective solution for high-speed in-home communication systems.

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.

Power-efficient impulse radio ultrawideband pulse generator based on the linear sum of modified doublet pulses

We propose a new and power-efficient impulse radio ultawideband (IR-UWB) pulse design concept. The proposed concept is based on a linear sum of modified doublet pulses. The proposed concept is both simulated and experimentally demonstrated. The experimental demonstration employs a photonic scheme that generates the designed pulse using two main steps, mainly optical shaping and differential detection. The optical shaping is performed using a single electro-optic modulator biased in the nonlinear portion of its transfer function, and the differential detection is performed using a balanced photodetector. The generated IR-UWB pulse is fully Federal Communications Commission compliant, even in the highly power-restricted global positioning system band. The proposed optical scheme has potential to be integrated on a compact optical chip and thus suitable for reliable, low-cost, high-speed, short-range UWB wireless access, such as in-building networks.