Bell Labs

About: Bell Labs is a based out in . It is known for research contribution in the topics: Laser & Optical fiber. The organization has 36499 authors who have published 59862 publications receiving 3190823 citations. The organization is also known as: Bell Laboratories & AT&T Bell Laboratories.

Optimal scheduling for two-processor systems

Abstract: Despite the recognized potential of multiprocessing little is known concerning the general problem of finding efficient algorithms which compute minimallength schedules for given computations and m?2 processors. In this paper we formulate a general model of computation structures and exhibit an efficient algorithm for finding optimal nonpreemptive schedules for these structures on two-processor systems. We prove that the algorithm gives optimal solutions and discuss its application to preemptive scheduling disciplines.

RMTP: a reliable multicast transport protocol

Abstract: This paper describes the design and implementation of a multi-cast transport protocol called RMTP. RMTP provides sequenced, lossless delivery of bulk data from one sender to a group of receivers. RMTP achieves reliability by using a packet-based selective repeat retransmission scheme, in which each acknowledgment (ACK) packet carries a sequence number and a bitmap. ACK handling is based on a multi-level hierarchical approach, in which the receivers are grouped into a hierarchy of local regions, with a designated receiver (DR) in each local region. Receivers in each local region periodically send ACKs to their corresponding DR, DRs send ACKs to the higher-level DRs, until the DRs in the highest level send ACKs to the sender, thereby avoiding the ACK-implosion problem. DRs cache received data and respond to retransmission requests of the receivers in their corresponding local regions, thereby decreasing end-to-end latency and improving resource usage. This paper also provides the measurements of RMTP's performance with receivers located at various sites in the Internet.

Theoretical and Experimental Effects of Spatial Dispersion on the Optical Properties of Crystals

Abstract: The classical dielectric theory of optical properties is a local theory, and results in a dielectric constant dependent only on frequency. This dielectric behavior can be written as a sum over resonances, each resonance occurring at a particular frequency. The spatial dispersion (i.e., nonlocal dielectric behavior) effect considered here is the effect of the wave-vector dependence of the resonant frequencies on optical properties. The additional boundary condition needed for the application of such a theory is discussed for the case in which the resonance is due to an exciton band and the wave-vector dependence to the finite exciton mass. Experimental data presented on the reflection peaks due to excitons in CdS and ZnTe exhibit gross departures from the reflectivities expected from classical theory. Particularly striking are sharp subsidiary reflectivity spikes. The departures from classical results are all well represented by calculations based on the theory of spatial resonance dispersion and a simple approximation to the drived boundary condition.

Separation of estimation and control for discrete time systems

Abstract: An attempt is made to coordinate the numerous results relating to separation of estimation and control in discrete time stochastic control theory. The results vary widely depending upon the assumptions about linearity, criteria, information pattern, constraints, and noise distributions. Some of the less well-known underlying concepts are discussed with the help of a fairly general model.

Compression of optical pulses chirped by self-phase modulation in fibers

Abstract: The use of self-phase modulation in a single-mode fiber to chirp an optical pulse, which is then compressed with a grating-pair compressor, has been shown to be a practical technique for the production of optical pulses at least as short as 30 fsec. We report the results of a theoretical analysis of this process. Numerical results are presented for the achievable compression and compressed pulse quality as functions of fiber length and input pulse intensity. These results are given in normalized units such that they can be scaled to describe a wide variety of experimental situations and can be used to determine the optimum fiber length and compressor parameters for any given input pulse. Specific numerical examples are presented that suggest that the technique will generally be useful for input pulses shorter than about 100 psec. For energies of a few nanojoules per pulse, the compressed pulse widths will typically be in the femtosecond regime.