Adaptively Modulated Optical Orthogonal Frequency Division Multiplexing Research Articles

Multi-electrode quantum-dot semiconductor optical amplifier as an intensity modulator of signals in optical communication systems

In this paper, we are going to exhibit the system performance using the single, double and three-electrode quantum-dot semiconductor optical amplifier as an intensity modulator (3E-QD-SOA-IM) of the adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) signals in the intensity-modulation direct-detection passive optical network (IMDD-PON) systems. Moreover, to compare the bit-rate versus transmission distance of the proposed fiber link model when using both configurations multi-electrode semiconductor optical amplifier intensity-modulator (ME-SOA-IM) and multi-electrode quantum-dot semiconductor optical amplifier intensity-modulator (ME-QD-SOA-IM), to study the improvement of the transmission capacity, distance reach and power efficiency when applying the proposed configurations for optical access networks for distances ranging from 20 km up to 120 km. The three-electrode configuration solved the nonlinearity of the two-electrode configuration and offered a considerably wider range of optimum operating conditions to achieve up to 35 Gbps. Furthermore, the 3E-QD-SOA-IM showed a better performance over the 3E-SOA-IM over all the 120 km, and a 5 Gbps enhancement in the bitrate with a 20 dB less optical input power at 20 km.

Increased Bit Rate Direct Modulation AMO-OFDM Transmission by Optical Injection Using Monolithically Integrated Lasers

Experimental and simulation work, presented in this letter, demonstrates for the first time how the monolithic integration of two single-mode lasers in a master-slave configuration, can substantially increase the achievable bit rate of a direct modulation adaptively modulated optical orthogonal frequency-division multiplexing (AMO-OFDM) system. The Levin-Campello algorithm is applied to select the OFDM bit and power loading scheme used for each system configuration. Improvement in terms of data throughput due to injection is measured for several transmission distances with the improvement in performance presented in terms of error vector magnitude per OFDM subcarrier.

Theoretical investigations of quantum-dot semiconductor optical amplifier enabled intensity modulation of adaptively modulated optical OFDM signals in IMDD PON systems

Extensive explorations are undertaken, for the first time, of the feasibility of utilizing quantum-dot semiconductor optical amplifier intensity modulators (QD-SOA-IMs) in cost-sensitive intensity-modulation and direct-detection (IMDD) passive optical network (PON) systems based on adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM). A theoretical QD-SOA-IM model is developed, based on which optimum QD-SOA-IM operating conditions are identified together with major physical mechanism considerably affecting the system performance. It is shown that, in comparison with previously reported SOA-IMs in similar transmission systems, QD-SOA-IMs cannot only considerably improve the AMOOFDM transmission performance but also broaden the dynamic range of optimum operating conditions. In particular, for achieving signal bit rates of >30Gb/s over >60km single mode fiber (SMF), QD-SOA-IMs offer a 10dB reduction in CW optical input powers injected into the modulators. In addition, QD-SOA-IMs can also be employed to compensate the chromatic dispersion effect.

Optical transmission performance in AMOOFDM downlink NG-PON systems using APD and pin receivers

Adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) modulation is experimentally evaluated using different photodiodes. A comparison is made between positive-intrinsic-negative (pin) and avalanche photodiode (APD) receivers in next generation passive optical network (NG-PON) downlink architecture. Direct modulation in transmission as well as direct detection in reception allows reducing the cost of the system. The results are obtained respecting the requirements of a class B+ optical budget. An additional amplifier is implemented to increase the reach of the pin photodiode. Although having a narrower bandwidth, the APD offers better performance than the pin. A bit rate of 10 Gbit/s can be reached for a distance of 60km with an optical budget of 30dB and without any optical amplifier.

Adaptive-Modulation-Enabled WDM Impairment Reduction in Multichannel Optical OFDM Transmission Systems for Next-Generation PONs

The transmission performance of multichannel adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) signals is investigated numerically, for the first time, in optical-amplification-free and chromatic-dispersion-compensation-free intensity-modulation and direct-detection systems directly incorporating modulated distributed feedback (DFB) lasers (DMLs). It is shown that AMOOFDM not only significantly reduces the nonlinear wavelength-division multiplexing (WDM) impairments induced by the effects of cross-phase modulation and four-wave mixing but also effectively compensates for the DML-induced frequency chirp effect. In comparison with conventional modulated optical orthogonal frequency-division multiplexing (OFDM), which uses an identical signal modulation format across all the subcarriers, AMOOFDM improves the maximum achievable signal transmission capacity of a central WDM channel by a factor of 1.3 and 3.6 for 40- and 80-km standard single-mode fibers, respectively, with the corresponding dynamic input optical power ranges being extended by approximately 5 dB. In addition, AMOOFDM also causes the occurrence of cross-channel complementary modulation format mapping among various WDM channels, leading to considerably improved transmission capacities for all individual WDM channels.

Adaptive Loading Algorithm Implemented in AMOOFDM for NG-PON System Integrating Cost-Effective and Low-Bandwidth Optical Devices

We experimentally investigate the transmission performance of a novel modulation based on a recently proposed technique of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) for next-generation passive optical network (NG-PON). This signal was generated by direct modulation of cost-effective and low-bandwidth commercially available distributed-feedback and vertical-cavity surface-emitting lasers. Using the Levin-Campello adaptive bit-loading algorithm for channel capacity optimization over AMOOFDM modulation to reach maximum transmission performance, we experimentally demonstrated that high bit rate can be transmitted in optical access network without the need for chromatic dispersion compensation and optical amplification on the link.

Transmission Performance of Adaptively Modulated Optical OFDM Modems Using Subcarrier Modulation over Worst-Case Multimode Fibre Links

An adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) modem using subcarrier modulation (SCM) (AMOOFDM-SCM) is proposed, for the first time, which consists of two conventional AMOOFDM modems in parallel with one operating at the baseband and the other being modulated onto an intermediate radio frequency (RF) carrier. Numerical simulations of the transmission performance of the AMOOFDM-SCM modems are undertaken in single-channel, optical amplifier-free, worst-case multimode fibre (MMF) links using intensity modulation and direct detection. It is shown that, based on practically available RF components, at least 64 Gb/s over 500 m and 37 Gb/s over 1000 m AMOOFDMSCM signal transmission is feasible in the aforementioned MMF links having 3-dB bandwidths as small as 292.5 MHz.km. In addition, when compared against the AMOOFDM technique, for achieving a required signal transmission capacity, AMOOFDMSCM also reveals significantly relaxed requirements on key component parameters, improved flexibility and robustness and more efficient use of MMF link spectral properties.

Statistical Investigations of the Transmission Performance of Adaptively Modulated Optical OFDM Signals in Multimode Fiber Links

Statistical investigations of the transmission performance of Adaptively Modulated Optical Orthogonal Frequency Division Multiplexing (AMOOFDM) are undertaken in single-channel, optical amplifier-free, Multimode Fiber (MMF)-based links using Intensity Modulation and Direct Detection (IMDD). Numerical simulations are performed using statistically constructed 1000 worst-case MMF links having 3-dB bandwidths varying in a range of 220-490 MHz middot km. It is shown that, by employing practically available devices, >30 Gb/s over 300-m AMOOFDM signal transmission is achievable in 99.5% of already installed MMF links, while by employing components that may be available in the future, the AMOOFDM technique is capable of supporting 100 Gb/s over 150-m signal transmission in 99.5% of already installed MMF links. In addition, it is confirmed, from a statistical point of view, that AMOOFDM has excellent flexibility and great robustness to different types of fibers and lasers, restricted launch conditions and practical implementation-related factors such as optical connector offset. It is also found that cyclic prefix and quantization are the key factors limiting the maximum achievable transmission performance of the AMOOFDM technique.

Optimization of adaptively modulated optical OFDM modems for multimode fiber-based local area networks [Invited

Focus Issue on Orthogonal-Frequency-Division Multiplexed Communications Systems and Networks The impact of a wide range of different parameters of various components involved in optical modems using adaptively modulated optical orthogonal-frequency-division multiplexing (AMOOFDM) on the transmission performance of AMOOFDM signals is explored thoroughly, in single-channel, unamplified, multimode-fiber (MMF)-based, intensity modulation and direct detection (IMDD) transmission links. Practically available optimum component parameters are identified, based on which the AMOOFDM modems are optimized. It is shown that the optimized AMOOFDM modems enable a >70% increase in the capacity versus reach performance without compromising link loss margins, in comparison with that achieved without modem optimization. In addition, the validity of the identified optimum parameters and the feasibility of the optimized AMOOFDM modems are also statistically verified for implementation in the vast majority of installed MMF links. Statistical investigations show that the optimized AMOOFDM modems can support >50Gbits/s signal transmission over 300m in 99.5% of already installed MMF links with loss margins of >7dB. Furthermore, it is also confirmed statistically that the optimized AMOOFDM modems have excellent performance flexibility and great robustness to various fiber and/or system implementation-related impairments.

Maximizing the Transmission Performance of Adaptively Modulated Optical OFDM Signals in Multimode-Fiber Links by Optimizing Analog-to-Digital Converters

Based on a comprehensive theoretical model of a recently proposed novel technique known as adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), investigations are undertaken into the impact of an analog-to-digital converter involved in the AMOOFDM modem on the transmission performance of AMOOFDM signals in unamplified intensity-modulation and direct-detection (IMDD) multimode-fiber (MMF)-based links. It is found that signal quantization and clipping effects are significant in determining the maximum achievable transmission performance of the AMOOFDM modem. A minimum quantization bit value of ten and optimum clipping ratio of 13 dB are identified, based on which, the transmission performance is maximized. It is shown that 40-Gb/s-over-220-m and 32-Gb/s-over-300-m IMDD-AMOOFDM signal transmission at 1550 nm with loss margins of about 15 dB is feasible in the installed worst case 62.5-mum MMF links having 3-dB effective bandwidths as small as 150 MHz middot km. Meanwhile, excellent performance, robustness to fiber types, and variation in launch conditions and signal bit rates is observed. In addition, discussions are presented of the potential of 100-Gb/s AMOOFDM signal transmission over installed MMF links

30-gb/s signal transmission over 40-km directly modulated DFB-laser-based single-mode-fiber links without optical amplification and dispersion compensation

Based on a recently proposed novel optical-signal-modulation technique of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), numerical simulations of the transmission performance of AMOOFDM signals are undertaken in directly modulated DFB laser (DML)-based single-mode-fiber (SMF) links without optical amplification and dispersion compensation. It is shown that a 30-Gb/s transmission over a 40-km SMF with a loss margin of greater than 4.5 dB is feasible in the aforementioned simple configuration using intensity modulation and direct detection (IMDD). In addition, the DFB-laser frequency chirp and the transmission-link loss are identified to be the key factors limiting the maximum achievable transmission performance of the technique. The first factor is dominant for transmission distances of < 80 km and the second one for transmission distances of > 80 km. It is also observed that fibers of different types demonstrate similar transmission performances, on which fiber nonlinear effects are negligible.

High-speed transmission of adaptively modulated optical OFDM signals over multimode fibers using directly Modulated DFBs

A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) is proposed, and a comprehensive theoretical model of AMOOFDM modems is developed. Numerical simulations of the transmission performance of the AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback (DFB) lasers (DMLs). It is shown that 28 Gb/s over 300 m and 10 Gb/s over 900 m transmission of intensity modulation and direct detection (IMDD) AMOOFDM signals at 1550 nm is feasible in DML-based links using MMFs with 3-dB effective bandwidths of 200 MHz/spl middot/km. Apart from a higher signal capacity, AMOOFDM also has a greater spectral efficiency and is less susceptible to different launching conditions, modal dispersion, and fiber types, compared with all existing schemes. In addition, a large noise margin of about 15 dB is also observed. The bits of resolution of analog-to-digital converters (ADCs) and the cyclic prefix of AMOOFDM symbols are the main factors limiting the maximum achievable performance, on which the influence of DMLs is, however, negligible under the optimum operating condition.

Transmission performance of adaptively modulated optical OFDM signals in multimode fiber links

A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) is proposed and numerical simulations of the transmission performance of AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback lasers (DMLs). It is shown that 28 Gb/s intensity modulation and direct-detection AMOOFDM signal transmission over 300-m MMFs is feasible in unamplified DML-based links having 3-dB bandwidths of 150MHz/km. In addition, AMOOFDM is less susceptible to modal dispersion and variation in launching conditions when compared with existing schemes.