We report on the generation of an optical comb of highly uniform in power frequency lines (variation less than 0.7 dB) using a silicon ring resonator modulator. A characterization involving the measurement of the complex transfer function of the ring is presented and five frequency tones with a 10-GHz spacing are produced using a dual-frequency electrical input at 10 and 20 GHz. A comb shape comparison is conducted for different modulator bias voltages, indicating optimum operation at a small forward-bias voltage. A time-domain measurement confirmed that the comb signal was highly coherent, forming 20.3-ps-long pulses.

We report a Nested Antiresonant Nodeless hollowcore Fiber (NANF) operating in the first antiresonant passband. The fiber has an ultrawide operational bandwidth of 700 nm, spanning the 1240-1940 nm wavelength range that includes the O-, S-, C-and L-telecoms bands. It has a minimum loss of 6.6 dB/km at 1550 nm, a loss ≤ 7 dB/km between 1465-1655 nm and ≤ 10 dB/km between 1297-1860 nm. By splicing together two structurally matched fibers and by adding single mode fiber (SMF) pigtails at both ends we have produced a ~1 km long span. The concatenated and connectorized fiber has an insertion loss of approximately 10 dB all the way from 1300 nm to 1550 nm, and an effectively single mode behavior across the whole spectral range. To test its data transmission performance, we demonstrate 50-Gb/s OOK data transmission across the O-to L-bands without the need for optical amplification, with bit-error-rates (BERs) lower than the 7% forward error correction (FEC) limit. With the help of optical amplification, 100-Gb/s PAM4 transmission with BER lower than the KP4 FEC limit was also achieved in the O/E and C/L bands, with relatively uniform performance for all wavelengths. Our results confirm the excellent modal purity of the fabricated fiber across a broad spectral range, and highlight its potential for wideband, low nonlinearity, low latency data transmission. Index Terms-Fiber optics communications, hollow core optical fibers, microstructured optical fibers.

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Abstract-We present nonlinear impairment mitigation of wavelength division multiplexed (WDM) signals, through optical phase conjugation (OPC). We conduct our experiments on a 400-km long installed fiber link equipped with erbium-doped fiber amplifiers (EDFAs), with the OPC placed close to the middle of the link. Our OPC configuration realizes efficient reuse of the signal bandwidth, avoiding the loss of half of the spectral band typical of most phase conjugating schemes. We demonstrate the operation of the system using both 16-and 64-quadrature amplitude modulation (QAM) signals and report Q-factor improvements up to 0.5 and 2.5 dB for 16-and 64-QAM, respectively.Index Terms-Fiber nonlinearity, nonlinear noise mitigation, optical fiber communication, optical phase conjugation, wavelength division multiplexing.

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