ABSTRACT
This paper describes the characterization of a novel directly modulated multi-section laser with a master-slave configuration. Amplitude and phase noise measurements show relative intensity noise values of around -150 dB/Hz and a 3-dB linewidth of around 3 MHz. The laser's suitability for optical access networks, enabled by the chirp reduction from the external injection locking, is shown by demonstrating unamplified 30 Gbit/s C-band transmission over 25 km and 50 km of single mode fiber using PAM4, as well as 30 Gbit/s PAM4 and PAM8 amplified transmission over 75 km.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
We report an injection locked flexible wavelength de-multiplexer (de-mux) that shows 24-h frequency stability of 1 kHz for optical comb-based elastic optical networking applications. We demonstrate 50 GHz, 87.5 GHz equal spacing and 6.25G-25G-50 GHz, 75G-50G-100 GHz unequal spacing for the de-multiplexer outputs. We also implement an unequally spaced (75G-50G-100 GHz), mixed symbol rate (12.5 GBaud and 40 GBaud) and modulation format (polarization division multiplexed quadrature phase shift keying and on-off keying) wavelength division multiplexed transmission system using the de-multiplexer outputs. The results show 0.6 dB receiver sensitivity penalty, at 7% hard decision forward error correction coding limit, of the 100 km transmitted de-mux outputs when compared to comb source seeding laser back-to-back.
ABSTRACT
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.
ABSTRACT
We investigate the effects of different phase noise processes of SGDBR laser on coherent systems. The SGDBR device operated well with QPSK modulation at 5 Gbaud, while the performance of 16-QAM was significantly degraded due to excess noise. The white FM noise mainly defines the ultimate performance of coherent reception, but the low frequency excess noise can potentially degrade the performance of systems that employ 16-QAM format at 5 Gbaud.
ABSTRACT
An experimental method for characterizing the time-resolved phase noise of a fast switching tunable laser is discussed. The method experimentally determines a complementary cumulative distribution function of the laser's differential phase as a function of time after a switching event. A time resolved bit error rate of differential quadrature phase shift keying formatted data, calculated using the phase noise measurements, was fitted to an experimental time-resolved bit error rate measurement using a field programmable gate array, finding a good agreement between the time-resolved bit error rates.
