We report a theoretical design analysis of domain-engineered periodically poled lithium niobate (PPLN) for wavelength conversion of near-infrared sources to generate coherent light in the visible spectral range. Our analysis on the spectral outputs show that with a proper design of the quasi phase matching (QPM) periods, tunable, multiple nonlinear optical processes can be simultaneously phase matched in a single segmented crystal. We show that a three-segment single PPLN crystal has potential to generate violet (432 nm), blue (490 nm) and orange (600 nm) wavelengths by simultaneous sum frequency and second harmonic generation processes. Such a design scheme has promising potential for a compact, robust and tunable multi-colored visible light source which can find various applications such as in biomedicine, high-density optical data storage and laser based color displays.

Distribution of timing and frequency signals in a fast-changing world requires unprecedented levels of stability for characterization. Transfer of frequency references over long distance without introducing any additional instability is of urgent concern for optical clock development. Choice of optical transmitter is critical to achieving accurate and stable RF clocks for end users. In this paper, we report the stability performance of the distributed feedback (DFB) laser and the Raman pump for transmitted clock signals. The DFB laser and the Raman pump were modulated with 2, 4, and 6 GHz RF clock signals from a signal generator and transmitted over 24.69 km SMF-Reach fiber. At 10 kHz offset frequency, we measured lowest phase noise of − 121.22 d B c / H z and highest spectra power of − 5.38 d B m at 2 GHz for the DFB laser. Transfer stabilities of 1.366 × 10 − 12 and 1.626 × 10 − 12 for 2 and 4 GHz, respectively, at 1000 s averaging time were achieved. This technique does not require additional amplifiers for long-distance frequency distribution, making it simple and economical, and hence satisfying the requirements for next-generation optical fiber networks.

No abstract

In this study, the influence of highly nonlinear fibre (HNLF) in Fibre optical parametric amplifier (FOPA) gain has been done using numerical simulations. Results shows that nonlinear coefficient, γ affect the gain flatness of a FOPA. It was also found that amplifier gain increase with increase in fibre length. These results help in improving the transmission capacity of long haul system and dense wavelength division multiplexing (DWDM).

Vertical cavity surface emitting lasers (VCSELs) are now major optical sources in optical communication and technology. The VCSEL-based transmission systems satisfy the next generation optical fibre access networks requirements such as low output power, low threshold currents, no optical amplification and use of single fibre for signal transmission. High speed and long wavelength 1550 nm VCSEL are attractive candidates for use in short distance transmission system due to its cost effectiveness and low drive currents. The performance of VCSEL, especially with respect to the low output power characteristics, has made significant progress. However, dispersion and attenuation is a major hurdle to VCSELs transmission at bit rate of 10 Gb/s and above. In this study, we experimentally and theoretically evaluate the capability of 1550 nm VCSEL to operate upto 10 Gb/s on G.655 and G.652 fibres. We present VCSEL characterization and BER performance as a function of received power. A 1550 nm VCSEL was directly modulated with 10 Gb/s NRZ PRBS 2 7-1 and transmitted over 25 km ITU. T G.652 and ITU. T G.655 fibres. Error free transmission (with bit error rate, BER, of 10-9) over 25 km G.655 single mode fibre (SMF) has been demonstrated. The Q factor was used theoretically to quantify the performance of the VCSEL. The Q factor increased with the increase in the output power at the receiver. High Q factor values of 6 and above were achieved when 1550 nm VCSEL was transmitted over G.655 fibre. These results show the feasibility of long-wavelength VCSELs in the deployment of enhanced optical access networks.