M. Deseada Gutierrez Pascual

Software reconfigurable highly flexible gain switched optical frequency comb source.

The authors present the performance and noise properties of a software reconfigurable, FSR and wavelength tunable gain switched optical frequency comb source. This source, based on the external injection of a temperature tuned Fabry-Pérot laser diode, offers quasi-continuous wavelength tunability over the C-band (30nm) and FSR tunability ranging from 6 to 14GHz. The results achieved demonstrate the excellent spectral quality of the comb tones (RIN ~-130dB/Hz and low phase noise of 300kHz) and its outstanding stability (with fluctuations of the individual comb tones of less than 0.5dB in power and 5pm in wavelength, characterized over 24hours) highlighting its suitability for employment in next generation flexible optical transmission networks.

100 km coherent Nyquist ultradense wavelength division multiplexed passive optical network using a tunable gain-switched comb source

We propose and experimentally demonstrate a long-reach Nyquist ultradense wavelength division multiplexed passive optical network using a tunable optical frequency comb source and a digital coherent receiver. Each of the six comb tones on a 12.5 GHz grid is modulated with a 12 Gbaud Nyquist polarization division multiplexed quadrature phase shift keyed signal which includes a 20% overhead for forward error correction. Unrepeated downlink transmission of 100 km is demonstrated at three different operating wavelengths across the C-band. A worst-case channel sensitivity of -35.3 dBm (59 photons/bit) is achieved at a bit error rate of 1.5 × 10-2, yielding a system loss budget of 35.7 dB.

Multi-wavelength coherent transmission using an optical frequency comb as a local oscillator

Steadily increasing data rates of optical interfaces require spectrally efficient coherent transmission using higher-order modulation formats in combination with scalable wavelength-division multiplexing (WDM) schemes. At the transmitter, optical frequency combs (OFC) lend themselves to particularly precise multi-wavelength sources for WDM transmission. In this work we demonstrate that these advantages can also be leveraged at the receiver by using an OFC as a highly scalable multi-wavelength local oscillator (LO) for coherent detection. In our experiments, we use a pair of OFC that rely on gain switching of injection-locked semiconductor lasers both for WDM transmission and intradyne reception. We synchronize the center frequency and the free spectral range of the receiver comb to the transmitter, keeping the intradyne frequencies for all data channels below 15 MHz. Using 13 WDM channels, we transmit an aggregate line rate (net data rate) of 1.104 Tbit/s (1.032 Tbit/s) over a 10 km long standard single mode fiber at a spectral efficiency of 5.16 bit/s/Hz. To the best of our knowledge, this is the first demonstration of coherent WDM transmission using synchronized frequency combs as light source at the transmitter and as multi-wavelength LO at the receiver.

Long reach UDWDM PON with SCM-QPSK modulation and direct detection

We demonstrate a 100km un-repeated downstream transmission based on a 12.5GHz wavelength tunable comb source with 1.25GBd SSB-SCM-QPSK data. The pilot tone enables direct detection and phase noise independence with error free performance at -20dBm.

InP photonic integrated externally injected gain switched optical frequency comb

We report on an InP photonic integrated circuit for the generation of an externally injected gain switched optical frequency comb. The device is fully characterized and generates a comb with frequency spacing ranging from 6 to 10 GHz, good noise properties that include relative intensity noise of <-130  dB/Hz and linewidth of 1.5 MHz, and a high phase correlation between comb lines. These characteristics, in conjunction with the compactness and cost efficiency of the integrated device, demonstrate the quality of the resultant comb source for numerous applications.

Injection Locked Wavelength De-Multiplexer for Optical Comb-Based Nyquist WDM System

We report a standalone four-output wavelength de-multiplexer (de-mux) using optical injection locking for simultaneous comb tone separation, amplification and power equalization. Optical amplification from -30 to 5 dBm per output wavelength is achieved. We illustrate the flexibility of the de-mux by separating two input combs with tone spacing of 12.5 and 6.25 GHz into 12.5-GHz spaced outputs. The system performance of the de-mux is demonstrated in a 100-km Nyquist ultra-dense wavelength division multiplexed network where the de-multiplexed comb tones are each encoded with 12-GBd Nyquist polarization division multiplexed quadrature phase shift keying. Experimental results indicate a worst case 1.5-dB receiver sensitivity penalty at 1.5e-2 bit error ratio for the transmitted comb tone channels when compared with the 400-kHz linewidth comb source seeding laser.

Parallel multi-wavelength intradyne reception using an optical frequency comb as a local oscillator

We investigate super-channel intradyne reception using an optical frequency comb as local oscillator (LO). We synchronize its center frequency and free spectral range with the corresponding parameters of the transmitter comb to compensate environmental drifts during operation.

Integrated Gain Switched Comb Source for 100 Gb/s WDM-SSB-DD-OFDM System

We demonstrate a 100 Gb/s short reach system using a multicarrier transmitter based on a gain switched monolithically integrated laser. An optical comb source with 12.5-GHz free spectral range is achieved by gain-switching an integrated passive feedback laser. The 100 Gb/s wavelength division multiplexed, single sideband, direct detection, orthogonal frequency division multiplexed (WDM-SSB-DD-OFDM) system operates over 25 km standard single mode fiber exhibiting a spectral efficiency of 1.8 b/s/Hz. Receiver sensitivity of -14.2 dBm is achieved after 25 km transmission. Performance optimization with phase and amplitude precompensation is employed to improve the SSB OFDM modulation thereby reducing the interchannel interference and overcoming the power fading induced by the optical filter. We also present a theoretical analysis of the SSB-OFDM modulation.

Cascaded Fabry-Pérot lasers for coherent expansion of wavelength tunable gain switched comb

We propose a simple potentially integrable configuration for expanding a wavelength tunable comb by cascading gain switched Fabry-Pérot lasers. A 10GHz spaced comb, exhibiting 13 coherent low-linewidth tones within a 3 dB window, and tunable over 20 nm is demonstrated.

Software-defined silicon-photonics- based metro node for spatial and wavelength superchannel switching

Due to the growing popularity of optical superchannels and software-defined networking, reconfigurable optical add-drop multiplexer (ROADM) architectures for superchannel switching have recently attracted significant attention. ROADMs based on micro-electro-mechanical system (MEMS) and liquid crystal-on-silicon (LCoS) technologies are predominantly used. Motivated by requirements for low power, high-speed, small area footprint, and compact switching solutions, we propose and demonstrate spatial and wavelength flexible superchannel switching using monolithically integrated silicon photonics (SiP) micro-ring resonators (MRRs). We demonstrate the MRRs’ capabilities and potential to be used as a fundamental building block in ROADMs. Unicast and multicast switching operation of an entire superchannel is demonstrated after transmission over 50 km of standard single mode fiber. The performance of each sub-channel from the 120 Gb∕s QPSK Nyquist superchannel is analyzed, and degradation in error vector magnitude performance was observed for outer sub-channels due to the 3 dB bandwidth of the MRRs, which is comparable with the superchannel bandwidth. However, all sub-channels for all switching cases (unicast, multicast, and bi-directional operation) exhibit performance far below the 7%FEClimit. The switching time of the SiPMRRchip is such that high-capacity superchannel interconnects between users can be set up and reconfigured on the microsecond time scale.