Optimization of semiconductor optical amplifiers for all optical wavelength conversion

In recent years a variety of experimental and theoretical work has been reported on the use of semiconductor optical amplifiers for high speed wavelength conversion. However little work has addressed the dynamic limitations of this conversion process in detail with a view to device optimization. In this paper, a detailed study of the conversion process is carried out in order to optimize device parameters and drive conditions for increased conversion speed and improved modulation index.

High-speed wavelength conversion utilizing birefringence in semiconductor optical amplifiers

This paper describes a novel technique whereby a mixture of cross-phase and cross-gain modulation effects in an SOA causes polarization rotation of a cw probe beam in the presence of a signal pulse, enabling the transmission of the probe through a polarizer to be controlled. The benefits of this approach are: 1) Very high extinction ratios present in the wavelength converted signal (>30 achieved); 2) A non-inverted wavelength converted signal, which is advantageous for chirp-compensation;2 3) A simple and stable experimental set-up, 4) Converted pulses which can be shaped to be faster than the input pulses.

Chirp limitation on high-speed wavelength conversion using semiconductor optical amplifiers

The cross-gain-saturation effect in SOAs, has been shown to enable robust high-speed wavelength conversion. Under strong electrical and optical pumping, conversion speeds in excess of 20 Gbit/s have been illustrated. However, the effect of chirp on transmission distance at such ultrahigh bit rates has not been studied theoretically in detail. This paper considers the chirp introduced on conversion, employing cross-gain saturation, and studies its dependence on amplifier drive current and signal power. It further shows how an increase in injected cw optical power can reduce chirp while improving conversion speed.

High speed wavelength conversion utilising an integrated amplifier/DFB laser

Wavelength conversion in the 1.55-μm regime was achieved for the first time in an integrated SOA/DFB laser by modulating the output power of the laser with a light beam of a different wavelength externally injected into the SOA section. In terms of speed, response times as low as 13ps were observed, though at the expense of reduced extinction ratio. Generally, these results indicate that operation in the 10s of GB/s should be possible.

Demonstration of 2.488Gb/s simultaneous all-optical wavelength conversion and tone reading/replacing in an integrated-SOA/DFB laser

A technique is demonstrated that allows for the wavelength conversion of data with both simultaneous monitoring and replacing of a wavelength identifying pilot tone. The technique should be upgradable to data rates of 10Gb/s and higher.

Highly flexible all-optical wavelength conversion at 2.488 Gbits/s using a multi-output-wavelength laser

An integrated multiwavelength grating cavity (MGC) laser fabricated by selective area regrowth is demonstrated. In addition to allowing wavelength conversion, the device can perform various important network functions such as space switching and multiplexing. The use of the device for these functions offers several advantages from a wavelength division multiplexing (WDM) network, such as flexibility, reduced component count, size, and the associated cost reduction.

Wavelength conversion based on an integrated semiconductor optical amplifier/DFB laser at 10 Gb/s with low input power

A study of the relative performance of an integrated semiconductor optical amplifier (SOA)/distributed feedback laser wavelength converter that can operate with negative penalties at 10 Gb/s rates is conducted. It is found that reduction of more than 25 times in required input powers are achieved when compared with laser or SOA converters.

All-optical routing using a 12×12 passive InP wavelength selective router and tuneable wavelength conversion

All-optical routing of 2.5Gbit/s WDM signals across two cascaded Optical Cross Connects(OXCs) with a penalty of only 0.6dB has been demonstrated using tuneable wavelength converters and a passive WDM router.

All optical wavelength conversion at 2.488 Gbits/s using the integrated multi grating cavity (MGC) laser

A novel integrated Multi-Wavelength Grating Cavity (MGC) laser has been used for multi-channel wavelength conversion at 2.488 Gbits/s. Functions demonstrated include conversion to multiple wavelengths, WDM multiplexing and 1×4 space switching.

1 × 4 space switching and simultaneous all-optical wavelength conversion at 2.488Gbit/s using a single monolithically integrated multiwavelength laser

A novel InGaAs/InGaAsP/InP integrated multiwavelength grating cavity laser is presented, which has been used to demonstrate space switching and simultaneous all-optical wavelength conversion at bit rates of 2.488 Gbit/s. This has been achieved using a single monolithically integrated device without the need for post-filtering to separate the converted signal from the input.

Wavelength conversion, regeneration and tone manipulation using integrated semiconductor lasers and amplifiers

An integrated semiconductor optical amplifier/distributed feedback (SOA/DFB) laser that show promise as a simple all-optical wavelength conversion device together with useful simultaneous functions such as 2R regeneration and the ability to remove a wavelength identifying tone is presented. Wavelength conversion performance at 20Gb/s and 40Gb/s can be obtained with this laser.

All-optical 3R regeneration and format conversion in an integrated SOA/DFB laser

Using a compact, integrated device at 2.488Gb/s, simultaneous NRZ to RZ format conversion and regeneration was achieved. The regenerated signal has a negative BER sensitivity of -1.5dB compared with a data signal transmitted down 101km of standard fiber.

Density, sp3 content and internal layering of DLC films by X-ray reflectivity and electron energy loss spectroscopy

A variety of hydrogenated and non-hydrogenated amorphous carbon thin films have been characterized by means of grazing-incidence X-ray reflectivity (XRR) to give information about their density, thickness, surface roughness and layering. We used XRR to validate the density of ta-C, ta-C:H and a-C:H films derived from the valence plasmon in electron energy loss spectroscopy measurements, up to 3.26 and 2.39 g/cm3 for ta-C and ta-C:H, respectively. By comparing XRR and electron energy loss spectroscopy (EELS) data, we have been able for the first time to fit a common electron effective mass of m*/me = 0.87 for all amorphous carbons and diamond, validating the `quasi-free' electron approach to density from valence plasmon energy. While hydrogenated films are found to be substantially uniform in density across the film, ta-C films grown by the filtered cathodic vacuum arc (FCVA) show a multilayer structure. However, ta-C films grown with an S-bend filter show a high uniformity and only a slight dependence on the substrate bias of both sp3 and layering.

All-optical 3R regeneration and wavelength conversion in an integrated SOA/DFB laser: Experiment and simulation

The simultaneous all optical 3R regeneration and format conversion in a simple, single integrated device was examined. The integrated device consisted of a semiconductor optical fiber (SOA) monolithically integrated with a distributed feedback (DFB) laser. Gain saturation was employed for the transmission of a data signal regenerated all-optically in the laser/amplifier device. The regeneration of the electrically filtered eye diagrams was observed by noise removal and extinction ratio-improvement by the device.