Reflective Electro-absorption Modulator Research Articles

SOA-REAM Assisted Synaptic Receptor for Weighted-Sum Detection of Multiple Inputs

Neuromorphic photonics is a promising research field due to its potential to tackle the limitations arising from the bottleneck of the von-Neumann computation architecture. Inspired by the characteristics and behavior of the biological brain, photonic neural networks are touted as a solution for solving complex problems that require GHz operation at low latency and low power consumption. An essential building block of such a neural network is a low-complexity multiply-accumulate operation, for which efficient functional implementations in the optical domain are sought for. Towards this direction, we present a synaptic receptor that functionally integrates weighting and signal detection. This optical multiply-accumulate operation is accomplished through a monolithic integrated semiconductor optical amplifier and reflective electro-absorption modulator, which together serve as a colorless frequency demodulator and detector of frequency-coded signals. Moreover, we show that two spike trains can be simultaneously processed with alternating signs and detected as a weighted sum. The performance of the proposed synaptic receptors is further validated through a low bit error ratio for signal rates of up to 10 Gb/s.

Reflective Electroabsorption Modulators for Beyond 25 Gb/s Colorless Transmissions

We present a complete characterization of reflective electroabsorption modulators (EAMs) monolithically integrated with semiconductor optical amplifiers (SOAs), components that are capable of operating beyond 50 Gb/s in the C-band. The devices are based on GaInAsP multiple quantum wells on InP substrate, leveraging semi-insulating buried heterostructure waveguide definition and butt-joint integration technologies. Different device configurations, based on 80- and 150-μm long EAMs, are fabricated and characterized in both static and dynamic modes. The frequency response of the 80 μm long EAM is still flat at 26.5 GHz (setup upper limit) whereas the 150 μm long EAM exhibits a 3-dB cutoff bandwidth of 23 GHz. A zero-chirp is achieved for EAM reverse bias voltages between -1.2 and -1.5 V depending on the wavelength. Under large-signal modulation, the frequency chirp induced by the shorter EAM is almost half that of the longer EAM, with their respective peak values being +1.5/-2 and +3.2/-3.7 GHz (rising/falling edges) at 1545 nm (-1.3 V bias, 2.6 V voltage swing). We obtained high dynamic extinction ratios of ~14.5 and ~8 dB from the longer and the shorter EAMs, respectively, when they are operated at 25 Gb/s using non-return-to-zero coding. Finally, we achieved 12 and 16 km colorless transmissions in the C-band (between 1530 and 1545 nm) over a standard single-mode fiber without equalization using the 150- and the 80 μm EAMs, respectively, with 4.5 and 2.5 dB dispersion penalties at a bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> .

High-Capacity Dynamic Indoor All-Optical-Wireless Communication System Backed up With Millimeter-Wave Radio Techniques

We propose a full-duplex dynamic indoor optical-wireless communication system using a crossed pair of diffraction gratings and photonic-integrated circuits with multicasting capability of 10-Gb/s on-off -keying and >40-Gb/s discrete-multitone data per user, backed up by a 60-GHz radio fallback system, with shared capacity of ∼40 Gb/s to realize reconfigurable and reliable high-capacity links to wireless users equipped with localization and tracking functionalities. The use of semiconductor optical amplifiers integrated with reflective electroabsorption modulators allows us to provide cost-efficient reflective transmitters at the user terminals in the upstream using centralized light sources and wavelength reuse technique. The 60-GHz radio fallback system allows us to cope with line-of-sight blocking in the optical-wireless links, thereby significantly enhancing the reliability of the wireless communication system.

High-Capacity Dynamic Indoor Network Employing Optical-Wireless and 60-GHz Radio Techniques

We demonstrate a hybrid radio–optical wireless communication system using a photonic integrated all-optical-cross-connect (OXC) chip to realize a highly reconfigurable and reliable bidirectional indoor wireless network that provides the ultimate capacity per user. By remote wavelength-tuning, narrow optical beams are directed to the users employing a passive two-dimensional beam steering module fixed at the ceiling in each room. Robustness regarding line-of-sight issues is achieved by implementing 60-GHz radio protection channels generated optically using a shared amplitude modulator via the OXC chip. The use of a 35-GHz reflective electroabsorption modulator (REAM) monolithically integrated with a semiconductor optical amplifier (SOA) chip is proposed for upstream wideband analog applications. The REAM-SOA provides similar performances as an REAM, but over a wide range of input optical powers and wavelengths. This mitigates the need for accurate control of the input signal, especially at remote sites where simplicity is strictly required. System experiments showed downstream optical-wireless transmission capacities of up to 35 Gb/s per user and 60-GHz protection channels with a capacity of 20 Gb/s. Upstream radio-over-fiber transmission rates of more than 35 Gb/s have also been achieved.

Integrated optical reflective amplified modulator for indoor millimetre wave radio‐over‐fibre applications

The use of a 35 GHz reflective electroabsorption modulator (REAM) monolithically integrated with a semiconductor optical amplifier (SOA) for indoor wideband analogue applications is demonstrated. Unlike REAMs, good performances over a wide range of input optical power and wavelength are observed, which mitigates the need for accurate control of the input signal, especially at remote sites where simplicity is strictly required. In addition, it provides amplification functions to compensate for the modulator insertion losses. The device exhibits an RF gain in excess of-22 dB and spuriousfree dynamic range of >103 dB Hz4/5. Implementing the rate-adaptive discrete-multitone modulation, 35 Gbit/s aggregate transmission speed is demonstrated for a short-range wideband subcarrier multiplexed radio-over-fibre system.

Equivalent Optical Bandwidth of Reflective Electro-Absorption Modulator Based Optical Source with a Broadband Seed Light for a 2.5 Gb/s and Beyond Signal Transmission

The impact of equivalent optical bandwidth on the performance of a system using a reflective electroabsorption modulator (R-EAM) based optical source has been experimentally evaluated with signals operating at 2.5 Gb/s and beyond. The equivalent optical bandwidth of our source with a broadband seed light was simply adjusted by using a bandwidth tunable optical filter. From the measurements, we have estimated the required equivalent optical bandwidth of our source for an error-free transmission (@ bit-error-rate of $10^{-12}$ ) and a forward error correction (FEC) threshold of $2{\times}10^{-4}$ .

Design and performance of 10-Gb/s L-band REAM-SOA for OLT Transmitter in next generation access networks

We present a 10-Gb/s L-band reflective electro-absorption modulator integrated with a semiconductor optical amplifier (REAM-SOA) having improved transmission performance at very low input power of seed light. To decrease the input power of seed light, the absorption characteristics of the REAM are adjusted to reduce the amplified spontaneous emission light returned into the SOA, suppressing the gain saturation effect of the SOA. At a considerably low input power of -16 dBm, the REAM-SOA exhibits a low transmission penalty of about 1.2 dB after 50-km SMF transmission. Over a wide input power range from -16 dBm to 5 dBm, a penalty of less than 1.6 dB is achieved at 50-km transmission.

Design Optimization of R-EAM-SOA for Long-Reach Carrier-Distributed Passive Optical Networks

Reflective electro-absorption modulators (R-EAMs) monolithically integrated with semiconductor optical amplifiers (SOAs) have strong potential as upstream transmitter in carrier-distributed long-reach passive optical networks (PONs). In these devices, the SOA provides the gain necessary to overcome the high loss of the PON power splitters, while the EAM allows the high speed and low chirp modulation required for long-reach PONs. It has previously been shown that purposely adding internal loss between the R-EAM and SOA compresses the burst-to-burst dynamic range on the upstream channels of the PON and that the SOA gain and the internal loss value between the SOA and the reflective surface are the key parameters which control this behavior. Dynamic range compression is an essential feature for carrier-distributed PONs, since both the carrier and the modulated signal experience the differential loss travelling through the optical distribution network of the PON. Other features of these modulators, which are also critical for the PON operation such as the output power and the patterning distortion, are also dependent on the SOA gain and internal loss value. In this paper, we demonstrate that careful design of the SOA gain and internal loss can provide an optimum balance between dynamic range compression, output power, and patterning distortion reduction. We model the R-EAM-SOA device in a network whose differential access loss is 15 dB. The dynamic range at the burst-mode receiver, using the optimized R-EAM-SOA, is found to be ∼12 dB, well within the capabilities of current burst-mode receiver designs. The optimum SOA gain is 24 dB, and the device has an internal loss in the range of 21 to 24 dB.

A Colorless Remote Antenna Unit for Bidirectional Photonic Antenna Remoting

A colorless (wavelength-independent) remote antenna unit (RAU) for bidirectional photonic antenna remoting is proposed and demonstrated, which is based on a reflective semiconductor optical amplifier electroabsorption modulator (SOA-EAM). Due to the gain saturation effect in the semiconductor optical amplifier (SOA) of the reflective SOA-EAM, the microwave signal carried by the downlink optical signal is received and effectively erased. Then, the electroabsorption modulator (EAM) converts the uplink RF signal to an optical signal, which is reflected back to the center office (CO) by the high-reflection coated facet of the device to provide the uplink service. No signal downconversion is needed since the modulation bandwidth of the EAM can reach tens of GHz. A proof-of-concept experiment is carried out. The RAU performs well in a bidirectional radio over fiber (ROF) system for providing 500 Mb/s wireless services centered at 2 GHz.

Performance evaluation of reflective electro-absorption modulator based optical source using a broadband light seed source for colorless WDM-PON applications

The performance of reflective electro-absorption modulator (R-EAM) based optical source has been evaluated for the use in high-capacity wavelength-division multiplexed passive optical networks (WDM-PONs). In our measurements, a broadband light source (BLS) was used as a seeding source for the cost-effective implementation of R-EAM based optical source. At first, a bit-error rate (BER) floor at 10(-6) was observed even in a back-to-back configuration with the BLS seeded R-EAM source. This is mainly because of the excess intensity noise (EIN) within BLS and the signal-to-noise ratio (SNR) degradation induced by a high insertion loss of R-EAM. To mitigate both effects of EIN and SNR degradation, a reflective semiconductor optical amplifier (RSOA) was also used for the implementation of our BLS seeded R-EAM source. Then, we have evaluated the impact of various noises, such as EIN, chromatic dispersion of transmission fiber and in-band crosstalk, on the system's performance using our BLS seeded R-EAM optical source. From the results, we have found that a 3-dB bandwidth of the BLS seeded R-EAM optical source should be wider than ~0.8 nm to achieve an error-free transmission of 1.25 Gb/s signal. We have also confirmed that there was a trade-off between the dispersion- and the in-band crosstalk-induced penalties due to the wide source bandwidth of our BLS seeded R-EAM source, like the cases of BLS seeded RSOA and Fabry-Perot laser diode (FP-LD) sources.

Experimental demonstrations of record high REAM intensity modulator-enabled 1925Gb/s real-time end-to-end dual-band optical OFDM colorless transmissions over 25km SSMF IMDD systems

Record-high 19.25Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) colorless transmissions across the entire C-band are experimentally demonstrated, for the first time, in reflective electro-absorption modulator (REAM)-based 25km standard SMF systems using intensity modulation and direct detection. Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting signal line rates of 9.75Gb/s and 9.5Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100MHz as well as DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically multiplexed for intensity modulation of a single optical carrier by an 8GHz REAM. The REAM colorlessness is experimentally characterized, based on which optimum REAM operating conditions are identified. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive transceiver optimization functions and live performance monitoring are fully exploited to optimize key OOFDM transceiver and system parameters. For different wavelengths within the C-band, corresponding minimum received optical powers at the FEC limit vary in a range of <0.5dB and bit error rate performances for both baseband and passband signals are almost identical. Furthermore, detailed investigations are also undertaken of the maximum aggregated signal line rate sensitivity to electrical sub-band power variation. It is shown that the aforementioned system has approximately 3dB tolerance to RF sub-band power variation.

Component and System Level Studies of Radiation Damage Impact on Reflective Electroabsorption Modulators for Use in HL-LHC Data Transmission

We investigate the radiation hardness of Reflective Electroabsorption Modulators (REAMs) for fluence levels up to 14 ×1015 24 GeV p/cm2 to explore the possibility of utilising REAMs for data readout at the High-Luminosity Large Hadron Collider (HL-LHC). The high fluence levels used in the experiment and the online spectral measurements carried out provide significant insight into the radiation damage mechanism. The radiation limits of an architecture based on REAMs are established and compared to LHC and HL-LHC fluence levels.

Mitigation of Rayleigh noise and dispersion in REAM-based WDM-PON using spectrum-shaping codes

This paper presents a novel technique capable of Rayleigh backscattering (RB) mitigation and chromatic dispersion (CD) compensation for wavelength-division-multiplexed passive optical network (WDM-PON). The reduction of the interference caused by RB and CD in the uplink based on reflective electro-absorption modulator (REAM) is realized by the proposed correlative level (CL) coding. We investigate the RB-induced interferometric crosstalk for different fiber lengths. 10 Gb/s and 20 Gb/s transmissions over 70 km and 35 km fiber are demonstrated using the CL codes of dicode and modified duobinary (MD), respectively. Significant improvement in system resilience to backscattered seed light is verified for both dicode and MD coding. MD-coded signal also exhibits considerable robustness against the effects of CD.

Mitigation of Rayleigh crosstalk using noise suppression technique in 10-Gb/s REAM-SOA

We demonstrate a mitigation of Rayleigh back-scattering (RBS) impact in 10-Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier (REAM-SOA). The technique is based on the intensity-noise suppression of the centralized incoherent seed-light, which enables smooth evolution of deployed DWDM applications. We exhibit the power penalty of less than 1 dB at the large RBS crosstalk value of about 8 dB when the optical power of seed-light is lowered about -10 dBm.

40 Gb/s Operation of SOA-REAM in Single-Feeder WDM-PON [Invited

The integrated semiconductor optical amplifier (SOA) with a reflective electro-absorption modulator (REAM) is a promising candidate for the colorless optical network unit in a wavelength-division-multiplexed passive optical network (WDM-PON), due to its low chirp and wide bandwidth. However, 40&#x00A0;Gb/s operation of REAMs (bandwidth &#x2264; 20&#x00A0;GHz) still encounters severe intersymbol interference. Furthermore, Rayleigh backscattering (RB) and discrete reflections cause strong beat noise in WDM-PONs with single-fiber loopback configuration. In this paper, we present two novel techniques based on electrical equalization for a 40-Gb/s single-feeder WDM-PON based on SOA-REAM. The first method is to employ partial-response (PR) signaling and a noise predictive maximum likelihood (NPML) equalizer at the upstream receiver. The other one combines correlative level (CL) pre-coding with partial-response maximum likelihood (PRML) equalization. We experimentally demonstrate a 40-Gb/s uplink of 20&#x00A0;km using a 20-GHz SOA-REAM in a WDM-PON by both PR-NPML and CL-PRML. The results also verify the superiority of PR-NPML over the previously reported equalizers. Moreover, compared with PR-NPML, CL-PRML further improves the system performance. Experiments prove that the tolerance to beat noise and the receiver sensitivity are enhanced by 4&#x00A0;dB and 0.8&#x00A0;dB, respectively, at a bit error ratio of 2&#x00D7;10&#x2212;4.

Experimental evaluation of a R-EAM and noise impact analysis for UWB and Wi-Fi transmission in RoF networks

The performance of a reflective electro-absorption modulator transceiver is assessed in terms of both slope efficiency (SE) and responsivity in a radio-over-fiber network. Different biasing schemes are analyzed, specifically zero bias (passive solution), bias for maximum SE, and bias for maximum responsivity. Finally, two case studies on multiband orthogonal frequency division multiplexing ultra-wide band and Wi-Fi are presented, for which the optimum setup parameters are determined.

Design and Demonstration of REAM-Based WDM-PONs With Remote Amplification and Channel Fault Monitoring

The use of reflective electro-absorption modulators (REAMs) as colorless upstream transmitters for wavelength-division-multiplexing passive optical networks is attractive for providing 10 Gb/s and above data rates. We address the feasibility of applying the remotely pumped optical amplifier to boost all upstream channels when REAMs are used at the optical network units. This scheme can avoid the use of more complicated devices, such as integrated REAMs with semiconductor optical amplifiers. The remote pumping scheme can simultaneously boost the upstream and downstream signals as well as the monitoring signals by the gain from the erbium-doped fiber and Raman amplification. The required pump power and the limitation on the seeding power are analyzed in order to optimize the bidirectional transmission performance for different access network spans.

An electroabsorption modulator-based network architecture for particle physics applications

The forthcoming increase in rate of data production and radiation levels, associated with the transitionto High-Luminosity Large Hadron Collider, necessitates a readout link upgrade. Such upgrade is also an opportunityto move to a more efficient network infrastructure through the introduction of new technologies and it is in lightof this that we explore the possibility of using a unified optical network architecture based on using ReflectiveElectroabsorption Modulators at the detector side. We evaluate the performance of the new architecture andinvestigate the way operating and environmental parameters such as wavelength and temperature affect it.

Dual-Operability and Bandwidth Partitioning Enabled by an ONU With Tandem-Modulator

An upgrade at the physical layer regarding unbundling and dynamic bandwidth provisioning of a wavelength division multiplexed access network is presented. The capability of a reflective modulator to act as a photodetector is exploited and allows a tandem configuration to be used at the optical network unit (ONU) for flexible switching of the detection and modulation branch. Consequently, a mechanism for service operator selection and for dynamic bandwidth partitioning up to twice the nominal data rate is provided. The scheme is experimentally evaluated for different kinds of modulators and shows, together with a full-duplex transmission at 10 Gb/s, additional operation modes, featuring unidirectional downstream and upstream burst-mode transmission with up to 20 Gb/s for ONUs based on a combination of a semiconductor optical amplifier and a reflective electro-absorption modulator.

OFDM-WiMAX Modulation of a Reflective Amplified Modulator in Radio-Over-Fiber Context

This letter presents experimental characterization of an integrated reflective electroabsorption modulator and semiconductor optical amplifier (REAM-SOA) device in the radio-over-fiber (RoF) context. Orthogonal frequency-division-multiplexing (OFDM) modulation condition optimizations have been carried out by varying the temperature, the voltage biasing of the modulator, and the current applied to the semiconductor amplifier.