Miguel V. Drummond

Photonic RF instantaneous frequency measurement system by means of a polarizatio-ndomain interferometer.

A new photonic RF instantaneous frequency measurement system is proposed and experimentally demonstrated. A frequency measurement independent of the optical input power and microwave modulation index is achieved by using the constructive and destructive ports of a polarization-domain interferometer. Experimental tests yield a peak-to-peak frequency error lower than 200 MHz for a frequency range of 1-18 GHz.

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.

Photonic True-Time Delay Beamforming Based on Polarization-Domain Interferometers

In this paper, we propose a novel photonic true-time delay beamforming system for phased array antennas. The system relies on tunable delay lines which are based on Mach-Zehnder delay interferometers (MZDIs) with tunable coupling ratio. As the MZDIs are implemented on the polarization domain, a single optical source and a single piece of polarization maintaining fiber are required. The proposed implementation is theoretically assessed and beam squinting is investigated by simulation. A proof-of-concept experiment that validates the operation principle of the proposed delay lines is presented.

Pump-linewidth-tolerant optical wavelength conversion for high-order QAM signals using coherent pumps

Optical wavelength conversion (OWC) is expected to be a desirable function in future optical transparent networks. Since high-order quadrature amplitude modulation (QAM) is more sensitive to the phase noise, in the OWC of high-order QAM signals, it is crucial to suppress the extra noise introduced in the OWC subsystem, especially for the scenario with multiple cascaded OWCs. Here, we propose and experimentally demonstrate a pump-linewidth-tolerant OWC scheme suitable for high-order QAM signals using coherent two-tone pumps. Using 3.5-MHz-linewidth distributed feedback (DFB) lasers as pump sources, our scheme enables wavelength conversion of both 16QAM and 64QAM signals with negligible power penalty, in a periodically-poled Lithium Niobate (PPLN) waveguide based OWC. We also demonstrate the performance of pump phase noise cancellation, showing that such coherent two-tone pump schemes can eliminate the need for ultra-narrow linewidth pump lasers and enable practical implementation of low-cost OWC in future dynamic optical networks.

GVD and PMD monitoring by means of SPM and XPM effects in a SOA

Fiber group-velocity dispersion and polarization mode dispersion must be dynamically compensated to avoid performance degradation of optical networks at high bit rates. Precise and reliable dynamic impairment compensation is enabled by optical impairment monitoring. In this paper, GVD and first order PMD monitoring with SOA is demonstrated. XPM is used to monitor the amount of GVD or PMD, whereas SPM allows finding the GVD sign.

Mobile fronthaul RoF transceivers for C-RAN applications

We address the development of mobile fronthaul (MFH) radio-over-fibre (RoF) transceivers with the capability to transport Digital RoF (D-RoF) signals for C-RAN applications. The coexistence of transport of D-RoF with legacy and the future Passive Optical Network (PON) systems, such as Next Generation PON 2 (NG-PON2) will be analysed. The preliminary experimental results of transmitting several D-RoF signals with high spectral efficiency and based on Sub-Carrier Multiplexing (SCM) techniques will be presented.

Phase-sensitive amplification in a single bi-directional PPLN waveguide.

We investigate phase-sensitive amplification (PSA) and phase regeneration of a binary phase-shift keying (BPSK) signal using a single periodically poled lithium niobate (PPLN) waveguide. The PPLN is operated bi-directionally in order to simultaneously achieve phase correlated signals and phase-sensitive (PS) operation. We use injection-locking for carrier phase recovery and a lead zirconate titanate (PZT) fiber stretcher to correct path length deviations in the in-line phase regenerator. We observe a trade-off between high PS gain provided by high pumping power and stability of the device.

Tunable Optical Dispersion Compensator Based on Power Splitting Between Two Dispersive Media

In this paper, we propose and experimentally demonstrate a novel tunable optical dispersion compensator (TODC). Dispersion compensation is achieved by splitting the input signal between two dispersive media and adding the resulting signals thereafter. Tunable compensation is attained by controlling the power splitting ratio of the input signal between both dispersive media. The frequency response of the TODC is theoretically assessed considering signal addition in the optical and electrical domains. The latter case is enabled by using optical single sideband (OSSB) modulation, which allows preserving the phase information of dispersive media output signals after direct detection. This is the only case experimentally tested, since it avoids stability problems related with coherent addition of optical signals. A TODC with a tuning range of -340 to 0 ps/nm was designed and experimentally assessed for a 40 Gb/s nonreturn-to-zero OSSB signal. The tunable power splitter consisted of an automatic polarization controller and a polarization beam splitter, which offered a tuning time lower than 150 ¿s. A bit error rate lower than 10-8 was measured on the entire compensation range with a maximum power penalty of 3.3 dB relatively to an SSB signal in back-to-back.

Photonic True-Time-Delay Beamformer for a Phased Array Antenna Receiver based on Self-Heterodyne Detection

In this paper, we propose a novel photonic true-time delay beamforming system for a phased array antenna receiver. The beamformer relies on simple tunable optical delay lines and also on self-heterodyne coherent detection. Each tunable delay line is implemented by a Mach-Zehnder delay interferometer with tunable coupling ratio, which allows varying the delay from 0 up to the delay of the interferometer. Self-heterodyne coherent detection allows achieving maximum sensitivity inherent to coherent detection, and also laser phase noise cancellation, photonic RF phase shifting, and photonic RF frequency downconversion. The proposed system is analytically described and numerically validated. Numerical results show that, considering a beamsteering range of ±30°, the system is able to beamform the signals received by N antenna elements with negligible distortion, thereby proving to be very promising for high-end phased array antenna receivers operating at high RF frequencies.

Flexible OTDM to WDM converter enabled by a programmable optical processor

We propose an OTDM to WDM converter which enables wavelength tunability, flexible OTDM tributary to WDM channel mapping and modulation format transparency. The converted signals are obtained by four-wave mixing (FWM) the input 160 Gb/s OTDM signal with a multi-wavelength sampling pulse train (SPT). The generation of the multi-wavelength SPT starts by multicasting an optical clock signal. The multicast pulses are then individually delayed and reshaped by a programmable optical processor (POP), resulting in flexible generation of the SPT. Error-free performance was achieved in different OTDM tributary to WDM channel mappings. In addition, intermediate rate conversion (2x80 Gb/s) was also achieved simply by reconfiguring the POP.