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We demonstrate that rectangular few-mode dielectric waveguides, fabricated with standard lithographic technique, can support on-chip propagation of optical vortices. We show that specific superpositions of waveguide eigenmodes form quasi-degenerate modes carrying light with high purity states of orbital angular momentum.

Vertical cavity surface emitting lasers fabricated with movable microelectromechanical mirrors can offer continuous single-mode wavelength tuning up to 100 nm with high efficiency and in a very small package. Wide tunability makes these diode lasers ideally suited for multispecies and high-density gas analysis and the first demonstrations of direct absorption spectroscopy and wavelength modulation spectroscopy have already been published. The performance of these systems could nevertheless be enhanced by the use of the new molecular dispersion spectroscopic methods, as heterodyne phase sensitive dispersion spectroscopy. This technique bases its operation on the detection of the profile of the refractive index of the sample under analysis, in contrast to traditional architectures based on the measurement of optical absorption, and this provides noticeable advantages. First, the method is normalization-free, and therefore, the characteristic issue of the nonmonotonic intensity profile during wavelength tuning of tunable vertical cavity surface emitting lasers is directly overcome. In addition, dispersion spectroscopy also provides an intrinsic linearity with concentration, high suitability for calibration-free operation, and an extended dynamic range that are very desirable features to have in an optical gas analyzer. In this Letter we present the first multispecies spectrometer based on a widely tunable vertical cavity surface emitting laser and heterodyne phase sensitive dispersion spectroscopy that is capable of operating in a tuning range of more of 80 nm for the simultaneous detection of several species. The authors would like to thank the Spanish Ministry of Economy and Competitiveness for supporting the projectunder the TEC-2014-52147-R grant and the Deutsche Forschungsgemeinschaft within the program Graduiertenkolleg TICMO (GRK 1037). The authors also acknowledge J. Cesar, S. Al-Daffaie, and A. Hajo for their contribution to the experiments.

We report on a new design of room-temperature terahertz quantum cascade lasers (THz QCLs) based on ZnMgSe/ZnSe material systems employing two-well design schemes with alternating quantum barrier heights and n-type delta-doping of the injector well. Our calculations show that this new THz QCLs achieves high optical gain at the emission frequency of 1.33 THz at room-temperature.

We report a new fully integrated THz Schottky detector based on vertically contacted high doped (1 · 1018/cm3) gallium arsenide (GaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact. Compared to Schottky diodes with evaporated metal contact it has lower capacitance (0.5 fF) for a high cut-off frequency as well as better zero-bias operation for a lower noise value.

A new type of continuous-wave (CW) terahertz (THz) photomixer was fabricated using a nitrogen-doped single layer graphene (N+SLG) powder and silver nanowire (Ag-NW of O 300 nm) on low-temperature-grown (LTG) GaAs. The new hybrid (N+SLG/Ag-NW) structure provides simple fabrication steps and better performance in terms of high current handling together with reliable operation. The THz output power itself can be increased due to high photocurrent of ∼ 1.8mA.

A new miniature black-body radiator with fast electrical modulation capability was fabricated using carbon nanotube (CNT) yarns (O 20–100 μm). The small diameter of the yarn allows a fast pulsed-modulation (> 100 Hz) without the need of a mechanical chopper. Furthermore, the single CNT yarn handles reliably high currents > 100 mA for high power operation. It can be even used in an array configuration with integrated filters and collimator lenses. Thus, these CNT yarns can be applied as electrically modulated broadband THz sources for fast monitoring of thin objects e.g. papers, envelopes and packages in production lines as well as in miniaturized secure thermal infrared communication systems [1] with increased bit rates.

II-VI compounds are promising materials for the fabrication of room-temperature terahertz devices due to their beneficial properties like as type-I conduction band alignment, high breakdown field strength (~331 kV/cm for ZnSe vs. ~80 kV/cm for GaAs), and higher values of the conduction band offset (1.5 eV for BeSe/ZnSe vs. 0.7 eV for AlAs/GaAs). In this paper we report on numerical study of the resonant tunneling transport in ZnBeSe/ZnSe/ZnBeSe symmetric and asymmetric resonant tunneling diodes (RTDs). The negative differential resistance feature is observed in the current-voltage characteristics of the ZnSe-based RTDs. It is found that the maximum of peak-to-valley ratio (PVR) of the current density is equal to 6.025 and 7.144 at 150 K, and to 1.120 and 1.105 at 300 K for the symmetric and asymmetric RTDs, respectively. The effect of barrier heights on the frequency and output power performance of RTD devices are studied and discussed.

In this paper an on-chip device capable of wavelength-selective generation of vortex beams is demonstrated. The device is realized by integrating a spiral phase-plate onto a MEMS tunable Fabry-Perot filter. This vortex-MEMS filter, being capable of functioning simultaneously in wavelength and orbital angular momentum (OAM) domains at around 1550 nm, is considered as a compact, robust and cost-effective solution for simultaneous OAM- and WDM optical communications. Experimental spectra for azimuthal orders 1, 2 and 3 show OAM state purity >92% across 30 nm wavelength range. A demonstration of multi-channel transmission is carried out as a proof of concept.

In this work, we have used a tunable VCSEL for high-speed optical data transmission. To obtain wide tunability, a MEMS-DBR is surface micromachined onto a short-cavity high-speed VCSEL operating at 1550 nm. Ultra-wide continuous tuning is realized with electro-thermal actuation of the MEMS with built-in stress gradient within SiOx/SiNy dielectric layers. The MEMS-VCSEL operates in single-mode with SMSR > 40 dB across the entire tuning range. Quasi-error-free transmission of direct-modulation at record 15 Gbps is reported for 20 nm tuning, showing the potential towards the standard requirements for the SFP+ modules in the tail-ends of the WDM transmission system.

In this paper, we experimentally demonstrate simultaneous wavelength and orbital angular momentum (OAM) multiplexing/demultiplexing of 10 Gbit/s data streams using a new on-chip micro-component-tunable MEMS-based Fabry-Perot filter integrated with a spiral phase plate. In the experiment, two wavelengths, each of them carrying two channels with zero and nonzero OAMs, form four independent information channels. In case of spacing between wavelength channels of 0.8 nm and intensity modulation, power penalties relative to the transmission of one channel do not exceed 1.45, 0.79 and 0.46 dB at the hard-decision forward-error correction (HD-FEC) bit-error-rate (BER) limit 3.8 × 10sup-3/supwhen multiplexing a Gaussian beam and OAM beams of azimuthal orders 1, 2 and 3 respectively. In case of phase modulation, power penalties do not exceed 1.77, 0.54 and 0.79 dB respectively. At the 0.4 nm wavelength grid, maximum power penalties at the HD-FEC BER threshold relative to the 0.8 nm wavelength spacing read 0.83, 0.84 and 1.15 dB when multiplexing a Gaussian beam and OAM beams of 1st, 2nd and 3rd orders respectively. The novelty and impact of the proposed filter design is in providing practical, integrable, cheap, and reliable transformation of OAM states simultaneously with the selection of a particular wavelength in wavelength division multiplexing (WDM). The proposed on-chip device can be useful in future high-capacity optical communications with spatial- and wavelength-division multiplexing, especially for short-range communication links and optical interconnects.

It has been shown earlier, that the injection locked semiconductor lasers enable effective amplitude noise suppression [1] and makes possible an extra level of signal multiplexing-orthogonal modulation [2], where DPSK and ASK NRZ channels propagate at the same wavelength [3]. In our work we use an injection-locked 1550 nm VCSEL as a slave laser providing separation of amplitude and phase modulations, carrying independent information flows. To validate the possibility of phase modulation extraction by an injection-locked VCSEL, an experimental setup shown in Fig. 1 has been built.

We experimentally demonstrate BER reduction and orthogonal modulation using an injection locked single-mode VCSEL. It allows us suppressing an amplitude noise of optical signal and/or double the capacity of an information channel.

We report continuously widely tunable InP-based pin-photodiodes by integrating a surface micromachined MEMS-based Fabry-Perot filter with FWHM/FSR of 0.3 nm/189 nm. Detection of 36 nm is obtained for WDM- or sensing-applications around 1550 nm.

We report full C-band tunable, 10 Gbit/s capability, directly modulated MEMS-VCSEL for next generation converged mobile fronthaul and backhaul applications. Bit error rates below 10(-9) were achieved over up to 40 km SSMF.

Today, even in access networks, data traffic is enormously increasing, a trend that causes existing passive optical network (PON) infrastructures to become bottlenecks in a tele- and data-communication infrastructure, which is aimed to be both broadband and seamless. Thus, two major objectives are considered for next-generation PONs (NG-PONs), i.e., first, bandwidth increase, and second, reach extension to reduce deployment costs. Here, we describe a new reach extension scheme that at the same time allows increasing the number of subscribers in the network. The amplification technique is based on a bidirectional semiconductor optical amplifier (SOA). It is shown that the extender configuration not only meets the bandwidth and budget requirements for NG-PONs but also remarkably improves them. Differential (quadrature) phase-shift keying (D(Q)PSK) signals are investigated in this paper. Hybrid wavelength-division multiplexing/time-division multiplexing (WDM/TDM) transmission up to 120-Gb/s downstream and 40-Gb/s upstream are experimentally demonstrated. The access budget of 33.4 dB is achieved at 10 Gb/s on every WDM channel in case of DPSK enabling a splitting ratio of 1:512 per wavelength. Furthermore, optical power budget of 40 dB is obtained when DQPSK is used, where a splitting ratio of 1024 per wavelength can be supported. Additionally, a cost-efficient chirped managed directly modulated laser scheme is proposed for DPSK signal generation in U.S. scenario enabling a high-power budget performance low-cost transmitter configuration, which appears suitable for NG-PON application. The proposed technique also alleviates nonlinear impairments [specifically, cross-phase modulation (XPM)], which appear in dense WDM transmission.

We report the results of an efficient solar pumped semiconductor laser system that uses high efficiency multi-junction photovoltaic cells and laser diodes in order to achieve the sunlight to laser light conversion efficiency of over 10% without any active cooling and concentration optics. Semiconductor lasers with wavelength from 445 nm to 1550 nm are powered directly by an array of photovoltaic (PV) cells under one sun illumination (100 mW/cm2). The maximum energy efficiency reaches 10.34% at 976 nm with an output power of 4.31 W. This system is inherently more efficient than direct solar pumped lasers that have been studied in the past and could play a key role in future renewable energy production and power beaming applications.

Continuous-wave (CW) terahertz (THz) photomixers are fabricated using 1-D nanocontacts on low-temperature-grown (LTG) GaAs and InGaAs, for operation wavelengths of 850 nm and 1550 nm, respectively. Silver (Ag) nanowire (NW) used as the nanocontact is aligned between the antennas patterned onto these photoconductive material by dielectrophoresis (DEP) technique. Reliable photocurrent measurements for both of these devices are experimentally demonstrated.

We present new kind of terahertz (THz) Schottky detectors based on high-doped GaAs and AlGaAs/GaAs high electron mobility transistor (HEMT) structure using silver (Ag) metallic nanowires (NWs) with different diameters as air-bridge contact between the antenna and Schottky anode. The dielectrophoresis allows a simple alignment of the NWs and fabrication of submicron anode contacts with high cut-off frequency as well as electric field enhancement at the Schottky contact for zero-bias operation. Furthermore, these metallic NWs can be integrated with semiconductor NWs for large scale, low cost THz detectors on any substrate, for example for security imaging application.

We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity >92% across a wavelength range of more than 30 nm.

We report a SOA-based fiber ring laser around 1.5 μm with an intracavity MEMS tunable Fabry-Perot filter for wavelength selection. Quasi-CW electro-thermal tuning of 103nm with a maximum output power of 1.3mW is reported.

This paper investigates a newly proposed spreading code-set based on the prime code (PC) families referred to as ‘transposed modified prime codes (T-MPC)’ for the enhancement of spectral efficiency of synchronous incoherent optical code-division multiple-access (OCDMA) networks. This code family increased the code-set cardinality up to twice of existing PC families’ size. This also implies that a greater number of users can be accommodated by the network. Since there is no longer a time-shift feature in T-MPC like in conventional modified prime codes (MPC), the code is not predictable and thus even more secure. Since the code structure is similar to MPC, its deployment in a system/network already running MPC will not require hardware modification. Due to the higher code utilization factor of T-MPC, a greater number of users are accommodated under certain bit-error rate (BER) resulting in remarkable improvement in the spectral efficiency (SE) and capacity. The T-MPC compatibility with low-weight energy-efficient MPC construction is also investigated. The BER and SE performances are analyzed and compared with existing code families. The results indicated that the T-MPC employment can improve up to 50% higher spectral efficiency.

We experimentally demonstrate optical retiming of a 10.7 Gb/s data stream utilizing the property of bound soliton pairs (or “soliton molecules”) to relax to an equilibrium temporal separation after propagation through a nonlinear dispersion alternating fiber span. Pulses offset up to 16 ps from bit center are successfully retimed. The results of the experiment are in agreement with numerical simulations. An enhanced version of this retiming scheme is analyzed using numerical simulations.

We demonstrate three novel all-optical signal processing methods for RZ-DPSK signals using a saturated SOA. The two logically opposite pulse streams from a demodulated noisy RZ-DPSK signal counter-propagate in the SOA. This configuration decreases the fluctuations in the demodulated marks while preventing the spaces from getting amplified. Photonic balancing provides functionality analogous to electrical balanced detection by reducing the required OSNR, and saturated asymmetric filtering removes the in-band ASE noise before detection. These methods are demonstrated experimentally by observing eye diagrams and BER measurements at 10.7 Gb/s and 22.3 Gb/s.

The performance of various modulation schemes for 100 Gbit/s single-channel serial transmission is investigated by means of numerical simulations. Different ASK and PSK modulation formats are compared in terms of total system reach for a 10 −9 BER requirement. RZ-DQPSK format with a 1920 km reach, without FEC and without the support of additional Raman amplification, outperforms all the other schemes including 10 × 10 Gbit/s NRZ DWDM inverse multiplexing.

Continuous-wave (CW) terahertz (THz) photomixing requires compact, widely tunable, mode-hop-free driving lasers. We present a single-mode microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) featuring an electrothermal tuning range of 64 nm (7.92 THz) that exceeds the tuning range of commercially available distributed-feedback laser (DFB) diodes (∼4.8 nm) by a factor of about 13. We first review the underlying theory and perform a systematic characterization of the MEMS-VCSEL, with particular focus on the parameters relevant for THz photomixing. These parameters include mode-hop-free CW tuning with a side-mode-suppression-ratio >50 dB, a linewidth as narrow as 46.1 MHz, and wavelength and polarization stability. We conclude with a demonstration of a CW THz photomixing setup by subjecting the MEMS-VCSEL to optical beating with a DFB diode driving commercial photomixers. The achievable THz bandwidth is limited only by the employed photomixers. Once improved photomixers become available, electrothermally actuated MEMS-VCSELs should allow for a tuning range covering almost the whole THz domain with a single system.

In this paper we discuss the bit pattern effect on optical clock signals recovered using tank circuits and using birefringent resonators. For the first time we compare the bit pattern dependence of the clock signals recovered from both schemes. We show that a birefringent resonator can recover the clock for the same number of consecutive zeros as the optical tank circuit. We also show quantitatively that the fluctuation of the clock signal amplitude is less for the birefringent resonator than the optical tank circuit. These results are obtained numerically and confirmed experimentally.

Clock recovery is a fundamental operation in digital telecommunications systems, where the receiver synchronizes itself to the transmitter timing. In optical clock recovery, this operation is made using optical signal processing methods. This paper reviews the physical principles and classifies the various optical clock recovery methods developed during the last 20 years.

We investigate a new parallel all-optical clock recovery scheme based on heterodyne beats of an optical sideband-filtered signal. The oscillating clock signal is recovered when the filtered sideband is combined with a stable local oscillator. The filtering is performed with an optical resonator, which by nature provides possibility for multiwavelength operation. The local oscillator could be realized by a multiwavelength laser, whose emission wavelengths are injection seeded with carrier wavelengths of the input data. The output signal of such a configuration benefits from a reduced bit-pattern effect and a stable offset level. The sideband filtering is demonstrated for 23 simultaneous channels at 100 GHz DWDM grid, each hosting a data stream of 10 Gbit/s.

In this paper, we propose an optimal signal constellation design algorithm suitable for the coherent optical nonlinear chromatic dispersion channels. The algorithm is a extended version of previously proposed algorithm for self phase modulation channel. Simulation results show significant improvement of bit error rate performances compared to the standard quadrature amplitude modulation format.

A new, simple, and cost efficient method is experimentally demonstrated to generate 6th order Gaussian derivative optically. Proposed technique is based on directly modulated semiconductor laser, optical filtering and chromatic dispersion of fiber transmission line.

We report frequency-tunable terahertz (THz) generation with a photomixer driven by an ultra-broadband tunable micro-electro-mechanical system vertical-cavity surface-emitting laser (MEMS-VCSEL) and a fixed-wavelength VCSEL, as well as a tunable MEMS-VCSEL mixed with a distributed feedback (DFB) diode. A total frequency span of 3.4 THz is covered in direct detection mode and 3.23 THz in the homodyne mode. The tuning range is solely limited by the dynamic range of the photomixers and the Schottky diode/photoconductor used in the experiment.

We report 12 Gbps transmission over 6.3 km SMF with a directly modulated widely tunable bulk micromachined MEMS-VCSEL. The MEMS is electrothermally actuated for a continuous tuning of >64 nm around 1560 nm center wavelength. Error-free BTB transmission is achieved at 10 Gbps for 50 nm tuning.

A new type of a fully integrated vertical nanocontact THz photomixer was fabricated on LTG-GaAs/n+GaAs /SI-GaAs wafer with a single silver nanowire of 60nm. The new vertical structure provides simple fabrication steps and better performance in terms of stability and antenna integration. The THz output power itself can be increased due to high photocur-rent of ∼7.5mA and small device capacitance of ∼0.6 fF.

A photocathode based on n-doped graphene emitters in series to a GaAs photoswitch was fabricated and used for pulsed field electron emission. The n-doped graphene array emits at low turn-on fields (< 3 V/µm). A fast photomodulation of the emission current with high on/off ratio ∼200 was achieved with a semi-insulating (s.i.) GaAs photoswitch in a diode configuration. Different laser sources were used for these investigations.

Optical UWB pulse generation and wireless propagation through antenna is investigated. Experimental BER results are presented. It is shown due to antenna characteristics monocycle pulse is converted into 3rd-order Gaussian derivative after wireless propagation.

We present polarization stable, tunable long-wavelength vertical-cavity-surface-emitting lasers (VCSELs) at 1.55 μm based on InP. The tuning is accomplished by a two-chip membrane mounting technique denoted as bulk-micro-machining. The membrane consists of a GaAs-based distributed Bragg reflector and represents the top mirror. By its electro thermal actuation, cavity tuning occurs. This results in a continuous wavelength shift. Polarization stability is achieved by an implemented semiconductor/air subwavelength grating (SWG) written in the top-most layers of the membrane facing the VCSEL eye after mounting process. The SWG integration is realized by a combination of holographic lithography, barrel, and reactive ion etching. The manufactured micro-electro-mechanical-system SWG-VCSELs show a continuous, polarization stable wavelength tuning of ~ 25 nm with a peak optical power of 4 mW fiber-coupled in an MMF and thresholds of 3-3.5 mA.

Metamaterials (MMs) are artificial media tailoring the propagation of light by a design of a unit cell (meta-atom, MA). There is the evident inclination in favor of numerical methods in the description of the optical properties of MMs at the expense of physical intuition. It is shown that complementary to the numerical ones, qualitative models can provide a deeper understanding of the basic physical processes. The phenomenological approach to the homogenization resulted in three possible representations of Maxwell equations: Casimir, Landau–Lifshitz, and new toroidal ones. The multipole approach has been formulated and extended to the case of coupling between MAs, including random MA positioning. It has been shown that the quadrupole moment inherently introduces nonlinear (second-order) material response. The multipole approach has been applied for the case of the quantum MM to the coupled carbon nanotubes, and for the case of MAs to regular and stochastic properties of the nanolaser (spaser), and monochromatic plane wave propagation in the MM consisting of nanolasers.

A novel bidirectional ultra-wideband over-fiber (UWBoF) system compatible with the wavelength-division-multiplexing (WDM) architecture is presented. In the proposed scheme, a 6th order Gaussian derivative is generated for UWB transmission in a downstream (DS) scenario, based on the directly modulated laser, accumulative chromatic dispersion in the transmission fiber and delay-line-interferometer (DLI). While the UWB signal is received from one of the DLI outputs, the other output is utilized to reuse the wavelength by injection locking a colorless Fabry-Perot laser diode (FP-LD). Due to the filtering effect of the FP-LD, a clear optical carrier without intensity modulation is then generated which can be used for upstream (US) baseband (BB) transmission by directly modulating the FP-LD. In order to eliminate the unwanted Rayleigh scattering induced noise in the bidirectional transmission, a dual - fiber transmission architecture is used. The principle of operation is explained. A symmetric transmission of 1.25 Gbps UWB over 60 km single mode fiber (SMF) is performed. Bit-error-rate (BER) measurements and eye diagrams for both down and upstream transmissions are presented.

We identified conditions for room-temperature operation of terahertz quantum cascade lasers (THz QCLs) where variable barrier heights are used on ZnSe/Zn1–xMgx Se material systems. The THz QCL devices are based on three-level two-well design schemes. The THz QCL lasers with alternating quantum barriers with different heights were compared with THz QCL laser structures with fixed quantum barrier heights. It is found that the THz QCL device with novel design employing variable barrier heights achieved the terahertz emission of about 1.45 THz at room-temperature (300 K), and has improved laser performance due to the suppression of thermally activated carrier leakage via higher-energy parasitic levels. Thus, THz QCL devices employing the design with variable barrier heights may lead to future improvements of the operating temperature and performance of THz QCL lasers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

A simple photocathode based on graphene nanoplatelets glued on semi-insulating (s.i.) GaAs was fabricated and used for field electron emission in a diode configuration. The graphene nanoplatelets act as field emitter array with low turn-on field. The photomodulation was achieved with a GaAs photoswitch in series to the bottom of the graphene nanoplatelet emitters. The position and power of the laser illumination (800 nm) was not critical for photomodulation.

With the use of SiO2/SiC based movable MEMS-DBR, the continuous tuning range of electrically pumped MEMS-VCSEL can be extended to > 140 nm. The high refractive index contrast of Δn > 1 between SiO2 and SiC reduces the needed number of layers (11 layers) and broadens the spectral width of the reflectivity (448nm for R > 99.5 %) by more than a factor of two compared to the material system SiO2/Si3N4 (23 layers / 216nm for R > 99.5 %), which has been used for the current world record continuous tuning range of 100nm of an electrically pumped MEMS-VCSEL. The smaller number of needed DBR-layers enables a significant reduction of the overall mirror thickness, which enables a further miniaturization of the device and thus an increase of the free spectral range (FSR), the ultimate limit for continuous wavelength tuning. In this paper we evaluate the performance advantages of using SiO2/SiC based MEMS-DBR for tunable VCSEL by using Transfer-matrix method simulations.

This paper proposes a budget extender which is at the same time burst power equalizer based on SOAs for upstream 10 Gbit/s PON that achieves 38 dB access budget and 16 dB dynamic range compression.

Different schemes of dispersion management for cascaded transmission systems composed of standard monomode fibers (SMFs) and dispersion compensating fibers have been studied considering the most essential boundary conditions for practical network design. Alternating ordering of the compensation sections is found to improve considerably the eye opening penalty for high amplifier spacings of 120 km.

The integration of ultra-wideband (UWB)-over- ber into passive optical network (PON) is of great interest as it bene ts the high bandwidth capability from optical network technologies and the high exibility from wireless network technologies. The later can only be done with a reasonable cost when a universal optical transmitter, which is capable of generation both UWB and PON signals, is available. Direct modulation of semiconductor laser was demonstrated to be suitable for high bit-rate PON systems, however the generation of UWB signals by this technique is still challenging. Using the chirp properties of directly modulated semiconductor lasers, UWB signals are generated. Di erent UWB signal waveforms and polarities are obtained. The received electrical spectra conform to the requirements of indoor UWB systems.

This paper experimentally investigates power budget extension configurations for WDM NG-PONs. Differential Phase Shift Keying (DPSK), and Differential Quadrature Phase Shift Keying (DQPSK) are considered. The budget enhancement techniques are based on Semiconductor Optical Amplifier (SOA). The paper thoroughly studies power budget enhancement for the two modulation formats and shows that the proposed configurations comply with current standards such as XG-PON1.

As demand for higher bandwidth is drastically increasing, bandwidth efficiency is going to be an issue in Passive Optical Networks (PONs). Moreover, network operators plan to reduce the number of central offices (COs) while extending the reach of the optical links, this enables them to reduce the deployment costs. This paper demonstrates the advantages of advanced modulation formats and a suitable configuration for the power budget enhancement of hybrid Wavelength Division Multiplexing-Time Division Multiplexing-Passive Optical Networks (WDM-TDM-PONs). The proposed technique can offer higher data rate, better bandwidth efficiency, and large number of customers. Differential (Quadrature) Phase Shift Keying (DQPSK) signals and Orthogonal Frequency Division Multiplexing (OFDM) will be considered. Simulations are performed using different modulation formats to evaluate the behavior of the proposed PON extender. Finally, Transmission of 1 Tbps WDM/TDM-OFDMPON over 60 km optical link is presented here. The simulation results, prove that 1600 users can be covered with 40 Gbps peak data rate.