Future high-speed optical communications networks operating at data rates in excess of 100Gbit/s per channel will require a sensitive and ultrafast technique for precise optical signal monitoring. The standard way of characterising high-speed optical signals to use a fast photodetector in conjunction with a high-speed oscilloscope. However, this method is limited to a maximum data rate of approximately 40Gbit/s. An alternative is to employ all-optical sampling techniques based on ultrafast optical nonlinearities present in optical fibres, optical crystals and semiconductors. One such nonlinearity is the optical-to-electrical process of Two-Photon Absorption (TPA) in a semiconductor. This paper presents an optical sampling technique based on TPA in a specially designed semiconductor microcavity. By incorporating the microcavity design, we are able to enhance the TPA efficiency to a level that can be used for high-speed optical sampling.
The ever-increasing demand for bandwidth in telecommunication networks is accelerating the use of optical fibre for broadband communication systems. In order to continue to increase the data rate of single channel optical communication systems, it is anticipated that Optical Time Division Multiplexing (OTDM) techniques will be used in future photonic systems. OTDM technologies should allow the transmission of information at data rates in excess of 100 Gb/s on a single wavelength, and by employing OTDM in conjunction with Wavelength Division Multiplexing (WDM), it should be possible to develop highly flexible, and spectrally efficient, multi-terabit/s optical networks. An essential element of any OTDM system will be the generation of sub-picosecond pulses to represent the data. The temporal and spectral purity of the optical pulses at the transmitter will essentially determine the overall data rate that can be achieved. In order to provide the multi-terabit/s data rates required, these pulses must be compressed into the pico- and sub-picosecond range. This paper will look in greater detail at this key element involved in an all-optical time division multiplexed system, namely the generation of sub-picosecond optical pulses, and it will explore the type of system performance that can be achieved given the spectral and temporal purity of the optical pulses.
A method for registering pairs of digital ophthalmic images of the retina is presented using anatomical features as control points present in both images. The anatomical features chosen are blood vessel crossings and bifurcations. These control points are identified by a combination of local contrast enhancement, and morphological processing. In general, the matching between control points is unknown, however, so an automated algorithm is used to determine the matching pairs of control points in the two images as follows. Using two control points from each image, rigid global transform (RGT) coefficients are calculated for all possible combinations of control point pairs, and the set of RGT coefficients is identified. Once control point pairs are established, registration of two images can be achieved by using linear regression to optimize an RGT, bilinear or second order polynomial global transform. An example of cross-modal image registration using an optical image and a fluorescein angiogram of an eye is presented to illustrate the technique.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.