ABSTRACT
A silicon-on-insulator microring with three superimposed gratings is proposed and characterized as a device enabling 3×3 optical switching based on orbital angular momentum and wavelength as switching domains. Measurements show penalties with respect to the back-to-back of <1 dB at a bit error rate of 10-9 for OOK traffic up to 20 Gbaud. Different switch configuration cases are implemented, with measured power penalty variations of less than 0.5 dB at bit error rates of 10-9. An analysis is also carried out to highlight the dependence of the number of switch ports on the design parameters of the multigrating microring.
ABSTRACT
We propose and demonstrate a technique for the generation of an optical comb with tunable line spacing in a periodically poled lithium niobate (PPLN) waveguide. The technique is implemented with four input continuous waves (CWs), which generate a 19-line comb tuned to the spacing of 25 and 20 GHz. We show that each additional CW switched on out of the quasi phase-matching band at the PPLN waveguide input generates the growth of six new lines. The performance of the comb is tested modulating the lines with a 40 Gb/s differential quadrature phase shift keying data, demonstrating error-free operation. Nonuniform spacing of the input seed CWs improves the efficiency of the line generation process.
ABSTRACT
The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system.
ABSTRACT
We propose and characterize a simple, integrable, and wavelength-preserving scheme able to groom a 40 Gbps (D)QPSK signal with a 20 Gbps OOK one into a 20 Gbaud (60 Gbps) 8-APSK signal. The proposed all-optical scheme is based on the second-order nonlinear signal-depletion effect in a single periodically poled lithium niobate (PPLN) waveguide. Performance of the device, characterized by means of BER measurements, attests error-free operation and a power penalty below 4.1 dB.
ABSTRACT
A colorless all-optical scheme performing the subtraction and addition of phases between phase-shift keying (PSK) signals exploiting cascaded sum and difference frequency generation in a periodically poled lithium niobate waveguide is introduced and experimentally demonstrated. The subtraction of phases of two 40 Gb/s differential quadrature PSK signals has been experimentally tested and performances have been analyzed in terms of bit error rate measurements.
