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.

Efficient path profiling

Abstract: A path profile determines how many times each acyclic path in a routine executes. This type of profiling subsumes the more common basic block and edge profiling, which only approximate path frequencies. Path profiles have many potential uses in program performance tuning, profile-directed compilation, and software test coverage. This paper describes a new algorithm for path profiling. This simple, fast algorithm selects and places profile instrumentation to minimize run-time overhead. Instrumented programs run with overhead comparable to the best previous profiling techniques. On the SPEC95 benchmarks, path profiling overhead averaged 31%, as compared to 16% for efficient edge profiling. Path profiling also identifies longer paths than a previous technique, which predicted paths from edge profiles (average of 88, versus 34 instructions). Moreover, profiling shows that the SPEC95 train input datasets covered most of the paths executed in the ref datasets.

High pressure H/sub 2/ loading as a technique for achieving ultrahigh UV photosensitivity and thermal sensitivity in GeO/sub 2/ doped optical fibres

Abstract: High pressure 'hydrogen loading' has been used to sensitise standard singlemode fibres, resulting in the largest reported UV induced index changes for low GeO/sub 2/ fibres. Grating bandwidths of 4 nm and peak nu ns of 5.9*10/sup -3/ have been reproducibly achieved. Substantial index changes have also been achieved by rapidly heating H/sub 2/ loaded fibres of various compositions.< >

Solid-state low-loss intracavity saturable absorber for Nd:YLF lasers : an antiresonant semiconductor Fabry-Perot saturable absorber

Abstract: We introduce a new low-loss fast intracavity semiconductor Fabry-Perot saturable absorber operated at anti-resonance both to start and sustain stable mode locking of a cw-pumped Nd:YLF laser. We achieved a 3.3-ps pulse duration at a 220-MHz repetition rate. The average output power was 700 mW with 2 W of cw pump power from a Ti:sapphire laser. At pump powers of less than 1.6 W the laser self-Q switches and produces 4-ps pulses within a 1.4-micros Q-switched pulse at an approximately 150-kHz repetition rate determined by the relaxation oscillation of the Nd:YLF laser. Both modes of operation are stable. In terms of coupled-cavity mode locking, the intra-cavity antiresonant Fabry-Perot saturable absorber corresponds to monolithic resonant passive mode locking.

`` Strong '' NP-Completeness Results: Motivation, Examples, and Implications

Abstract: The NP-completeness of a computational problem ~s frequently taken to unply its \"mtractabthty\" However, there are certain NP-complete problems mvolvmg numbers, such as PARTITION and KNAPSACK, which are considered by many practitioners to be tractable The reason for this IS that, although no algontluns for solvmg them in tune bounded by a polynomial m the mput length are known, algorithms are known which solve them m tune bounded by a polynomial m the input length and the magmtude of the largest number an the given problem mstance. For other NP-complete problems mvolvmg numbers it can be shown that no such \"pseudopolynomml tune\" algonthra can exist unless P = NP. In this paper we provide a standard framework for stating and proving \"strong\" NP-completeness results of this sort, survey some of the strong NP-completeness results proved to date, and indicate some unphcauons of these results for both opumlzatlon and approximaUon algontluns