Single Electroabsorption Modulator Research Articles

Broadband optical frequency comb generation based on single electro-absorption modulation driven by radio frequency coupled signals

Broadband optical frequency comb (OFC) generation based on a single electro-absorption modulator (EAM) is proposed. The EAM is driven by a radio frequency (RF) multi-frequency signal generated by a multiplication coupler composed of an electrical power splitter and an arithmetic circuit. Thus the number of comb-lines of the generated OFC can be increased. A complete theoretical model of OFC generation by an EAM driven by nth power of the RF source is established, and the performance of the OFC is analyzed by using OptiSystem software. The results show that, the number of comb-lines of the OFC is positively correlated with the number of multiplication of the RF source signal. The frequency spacing of the comb-lines is twice the frequency of the RF source signal and is tunable by adjusting the frequency of the RF source signal. Increasing chirp factor and modulation index of EAM could increase the number of comb-lines of the generated OFC. The amplitude of the RF source signal had little impact on the flatness of the OFC and the average OFC power. The scheme developed is not only simple and low-cost, but also can produce a large number of comb-lines.Graphical

Optical Pre-Emphasis by Cascaded Graphene Electro Absorption Modulators

A simple optical circuit made by a cascade of two graphene-on-silicon electro absorption modulators (EAMs) of different length is used for the optical pre-emphasis of 10 Gb/s non-return-to-zero (NRZ) signals by delay-inverse-weight compensation. Transmission up to 100 km on single mode fiber (SMF) without dispersion compensation is reported, showing also the large performance advantage (6 dB in back-to back and around 5 dB in transmission) in respect of the conventional single EAM transmitter configuration.

4:1 Silicon Photonic Serializer for Data Center Interconnects Demonstrating 104 Gbaud OOK and PAM4 Transmission

With next-generation optical interconnects for data centers aiming for 0.8 Tb/s or 1.6 Tb/s, 100 Gbaud capable transmitters from a single-laser source will become indispensable. However, these lane rates would require bandwidths of 70 GHz or more, doubling the bandwidth requirements of the electrical and optical components with respect to the fastest current generation of optical interconnects running at 53 Gbaud pulse-amplitude modulation (PAM-4). In this paper, we propose an integrated 4:1 optical serializer topology to achieve 104 Gbaud On-Off Keying (OOK) and PAM-4 transmission using only quarter rate components at the transmitter. We show 104 (208) Gbit/s OOK (PAM4) transmission using four GeSi electro-absorption modulators (EAMs) over 1 km of single-mode fiber (SMF). For 104 Gbaud OOK, clearly open eyes are obtained, while for PAM-4 the performance is limited by the nonlinear E/O-transfer function of the EAM. However, adding pre-emphasis in the electrical driver or replacing the single EAM with our previously demonstrated optical DAC topology—consisting of two EAMs in parallel with a 90° phase difference between each—could substantially improve these results. Additionally, we discuss the possibility of a four channel transmitter (4 × 208 Gb/s) from a single mode locked laser, amounting to a 832 Gb/s rate based on the current demonstrator.

Photonic Instantaneous Microwave Frequency Measurement System Based on Signal Remodulation

A novel photonic instantaneous microwave frequency measurement system based on signal remodulation is proposed and experimentally demonstrated. Modulation and remodulation are achieved using a single electroabsorption modulator operating bidirectionally. The RF power and frequency are derived from the RF tone powers of the modulated and remodulated signals, respectively. The incoherent operation principle of the proposed system enables a high resolution measurement with reduced ambiguity over a large frequency range.

Novel ultra-wideband (UWB) photonic generation through photodetection and cross-absorption modulation in a single electroabsorption modulator

We propose and demonstrate, by proof of concept, a novel method of ultra-wide band (UWB) photonic generation using photodetection and cross-absorption modulation (XAM) of multiple quantum wells (MQW) in a single short-terminated electroabsorption modulator (SEAM). As an optical pump pulse excite the MQWs of SEAM waveguide, the probe light pulse with the same polarity can be generated through XAM, simultaneously creating photocurrent pulse propagating along the waveguide. Using the short termination of SEAM accompanied by the delayed microwave line, the photocurrent pulse can be reversed in polarity and re-modulated the waveguide, forming a monocycle UWB optical pulse. An 89 ps cycle of monocycle pulse with 114% fractional bandwidth is obtained, where the electrical power spectrum centered at 4 GHz of frequency ranges from 0.1 GHz to 8 GHz for -10 dB drops. Meanwhile, the generation processing is also confirmed by observing the same cycle of monocycle electrical pulse from the photodetection of SEAM. The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.

Generation of Different Modulation Formats Using Sagnac Fiber Loop With One Electroabsorption Modulator

A simple structure is proposed to generate different modulation formats using a single electroabsorption modulator (EAM). The configuration is based on a Sagnac loop containing two polarization controllers and an EAM which modulates the clockwise and counterclockwise propagating waves inside the Sagnac loop. Measured results demonstrate switchable single-sideband suppression for both reflected and transmitted signals. The second-order harmonic suppression and carrier suppressed modulation are also achieved. A simple analysis explains most of the observed effects.

Simultaneous four-wave mixing and cross-absorption modulation inside a single EAM for high-speed optical demultiplexing and clock recovery

We report a novel technique that utilizes a single electroabsorption modulator (EAM) to perform simultaneous four-wave mixing (FWM) demultiplexing and all-optical timing extraction. The extracted timing, using fast cross-absorption saturation, is used to recover the subharmonic optical clock from 80-Gb/s data. Investigations of the single-pump FWM process in EAM shows a wide wavelength detuning range with almost flat FWM efficiency at large detuning. Enhancement of FWM efficiency with reverse bias of the EAM was observed.

40-GHz optical-pulse generation based on electroabsorption modulator driven by low-power MMIC

This paper reports on the design of an optical-pulse source at a 40-Gb/s repetition rate integrating a single electro-absorption modulator (EAM) sinusoidally driven by a 40-GHz low-power MMIC driver specifically designed to match the electro-optical response of the EAM. The 40-GHz MMIC HEMT driver has been designed to optimize the required control voltage of the InP-based MQW-EAM in order to generate optical pulses with a narrow pulse width and high extinction ratio from a very-low-power drive. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 158–160, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21111

Photonic‐microwave harmonic mixers based on electroabsorption modulators

AbstractTwo harmonic photonic‐downconversion schemes employing electroabsorption modulators are proposed and experimentally demonstrated. Harmonic downconversion of 34‐Mb/s data modulated onto a 9.5‐GHz signal has been performed using (i) a single electroabsorption modulator, (ii) a Mach–Zehnder modulator and an electroabsorption modulator in series. Error‐free operation for both schemes is demonstrated after transmission of the IF signal through a 25‐km fiber‐optic link for harmonic orders of up to three. The influence of the biasing point of the modulator on the overall performance of both photonic downconversion schemes is discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 361–364, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20141

All-optical signal regeneration with wavelength multicasting at 6�10 Gb/s using a single electroabsorption modulator

All-optical signal regeneration with wavelength multicasting has been demonstrated using cross-absorption modulation in a single electroabsorption modulator for the first time. We show that the input signal wavelength can be simultaneously converted to 6 different wavelengths at 10 Gb/s with signal regeneration. The output extinction ratio, the linewidth, and the pulse shape show a significant improvement. A negative power penalty of 2 dB is obtained at 10-9 bit-error-rate level.

Subharmonic optical clock recovery from 160 Gb/s using time-dependent loss saturation inside a single electroabsorption modulator

A single electroabsorption modulator (EAM) is utilized to perform subharmonic all-optical timing extraction from 160 Gb/s. The extraction technique is based on fast time-dependent loss saturation inside the EAM. The extracted timing is used for optical clock recovery with /spl les/340 fs of timing jitter. The clock recovery technique is bit-rate flexible, and the bit-error-ratio measurements reveal an error-free operation with no receiver sensitivity penalty.

All-optical wavelength conversion with multicasting at 6×10 Gbit/s using electroabsorption modulator

All-optical wavelength conversion with multicasting has been demonstrated with a single electroabsorption modulator based on cross-absorption modulation. It is shown that the input signal wavelength can simultaneously convert to six different wavelengths at 10 Gbit/s, and the relation between the power penalty and the number of simultaneously operating channels is investigated.

Ultra-low-jitter multiwavelength synchronised optical pulse source for C-, L- and U-bands

A novel self-starting optoelectronic oscillator that uses a single electroabsorption modulator in a fibre-extended cavity to generate synchronised optical pulses simultaneously at multiple wavelengths is demonstrated. We have generated 10 GHz-rate optical pulses simultaneously at eight wavelengths in the C-band, each with the lowest timing jitter (42 fs in the 100 Hz to 1 MHz range) reported to date for self-starting sources. Potential for operation in the L- and U-communication bands is also demonstrated.

Standing-wave enhanced electroabsorption modulator for 40-GHz optical pulse generation

Compact 40-GHz optical pulse generators are crucial to the implementation of practical 160-Gb/s optical time-division-multiplexing systems with 40-Gb/s electrical time-division-multiplexing tributaries. In this letter, we report on a novel standing-wave enhanced mode of the electroabsorption modulator (EAM) which can improve the performance of a single EAM for 40-GHz pulse generation. Both experimental and theoretical results indicate that the distributed effect plays an important role in the high-frequency operation of the EAM and the length of the microwave termination line must be adjusted properly to maximize the performance.

All-optical timing extraction with simultaneous optical demultiplexing from 40 Gb/s using a single electroabsorption modulator

We demonstrate a technique for performing optical time-division demultiplexing with simultaneous all-optical timing extraction using a single electroabsorption modulator (EAM). The technique is based on time-dependent transmission of the all-optically controlled EAM using a counterpropagation scheme between the data and clock optical pulses. The extracted timing is used in a feedback configuration to recover the optical clock. The bit error ratio measurement for demultiplexing from 40 Gb/s (4/spl times/10 Gb/s, 2/sup 31/-1 pseudorandom bit sequence) to 10 Gb/s showed an error-free operation with a 3.2-dB power penalty. The recovered clock-timing jitter is less than 200 fs.

Simultaneous all-optical demultiplexing of a 40-Gb/s signal to 4 x 10 Gb/s WDM channel's using an ultrafast fiber wavelength converter

We demonstrate simultaneous demultiplexing of a 40-Gb/s optical time division multiplexed stream to four 10-Gb/s data streams, each on a different wavelength, using a single ultrafast nonlinear fiber wavelength converter. The wavelength converter employs cross-phase modulation in a dispersion-shifted fiber and utilizes control pulses generated at four wavelengths by a single electroabsorption modulator. This technique can be scaled to demultiplex a very high bit-rate signal to multiple wavelength division multiplexed channels simultaneously using just one electroabsorption modulator and one fiber based wavelength converter. Additionally broad control pulses with limited extinction ratio do not adversely affect the performance of the demultiplexer. For a control pulsewidth of 11-12 ps, the measured power penalty is <1.5 dB. Increasing the control pulsewidth to 14 ps incurs an additional power penalty of only 0.5 dB.

Optical 3R regeneration using a single EAM for all-optical timing extraction with simultaneous reshaping and wavelength conversion

The authors demonstrate a technique that utilizes a single electro-absorption modulator (EAM) to perform simultaneous all-optical timing extraction, reshaping, and wavelength conversion. The extracted timing is used to generate an error signal that is used to recover the optical clock. The same EAM is used to encode the incoming data onto the retimed clock pulses in order to perform 3R regeneration and wavelength conversion. The system performance was tested using a 2/sup 31/-1 pseudorandom binary sequence (PRBS) data running at 10 Gb/s with a 3.3-ps pulsewidth. The input data was degraded by adding a 500-kHz timing jitter and reducing the optical signal-to-noise ratio (SNR) to 18 dB. The 3R regenerated data showed a 4.7-dB improvement in power penalty and 20-dB improvement in optical SNR. The calculated timing jitter of the recovered clock is less than 230 fs.

Simultaneous modulation of several WDM channels using a single electro-absorption modulator

A characterisation has been undertaken of the simultaneous modulation of several fibre optical WDM channels employing a single electro-absorption modulator operating at 10 GHz. This experimental investigation has demonstrated that sub 8 ps pulses can be generated over a 19 nm wavelength range under fixed operating conditions.

Simultaneous demultiplexing and clock recovery using a single electroabsorption modulator in a novel bi-directional configuration

A single electroabsorption modulator was used to demultiplex a 10 Gbit/s channel from a 40 Gbit/s OTDM data stream, whilst simultaneously recovering the 10 GHz electrical clock. This was achieved using a new bi-directional operation of the EA modulator, combined with a simple phase-locked loop feedback circuit. Excellent system performance was achieved, indicating that operation up to and beyond 100 Gbit/s is possible using current technology.

Simultaneous two-channel OTDM demultiplexing using a single electroabsorption modulator in a novel bi-directional configuration

A single electroabsorption modulator was used to simultaneously demultiplex two 10 Gbit/s channels from a 40 Gbit/s OTDM data stream. Error-free operation was observed, and the effects of incoherent interference between the demultiplexed channel and residual facet reflections investigated.