Wavelength-division-multiplexing (WDM) technology is now recognized as one of the key technologies in optical communications systems. This is because it has great potential to enhance system design and flexibility. This paper reviews state-of-the-art optical multi/demultiplexers (MUX/DEMUX) and WDM system design. Various system applications are also summarized.

Review and status of wavelength-division-multiplexing technology and its application

This is the third of a series of articles reporting critically evaluated rotational–vibrational line positions, transition intensities, and energy levels, with associated critically reviewed labels and uncertainties, for all the main isotopologues of water. This paper presents experimental line positions, experimental-quality energy levels, and validated labels for rotational–vibrational transitions of the most abundant isotopologue of water, H216O. The latest version of the MARVEL (Measured Active Rotational–Vibrational Energy Levels) line-inversion procedure is used to determine the rovibrational energy levels of the electronic ground state of H216O from experimentally measured lines, together with their self-consistent uncertainties, for the spectral region up to the first dissociation limit. The spectroscopic network of H216O containstwo components, an ortho (o) and a para (p) one. For o-H216O and p-H216O, experimentally measured, assigned, and labeled transitions were analyzed from more than 100 sources. The measured lines come from one-photon spectra recorded at room temperature in absorption, from hot samples with temperatures up to 3000 K recorded in emission, and from multiresonance excitation spectra which sample levels up to dissociation. The total number of transitions considered is 184 667 of which 182 156 are validated: 68 027 between para states and 114 129 ortho ones. These transitions give rise to 18 486 validated energy levels, of which 10 446 and 8040 belong to o-H216O and p-H216O, respectively. The energy levels, including their labeling with approximate normal-mode and rigid-rotor quantum numbers, have been checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators as well as against previous compilations of energy levels. The extensive list of MARVEL lines and levels obtained are deposited in the supplementary data of this paper, as well as in a distributed information system applied to water, W@DIS, where they can easily be retrieved.

/pdf/iupac-critical-evaluation-of-the-rotational-vibrational-xnjkox60dk.pdf

IUPAC critical evaluation of the rotational-vibrational spectra of water vapor, Part III: Energy levels and transition wavenumbers for H216O

This is the first part of a series of articles reporting critically evaluated rotational– vibrational line positions, transition intensities, pressure dependence and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. The present article contains energy levels and data for line positions of the singly substituted isotopologues H2

/pdf/iupac-critical-evaluation-of-the-rotational-vibrational-3t2w3miivs.pdf

IUPAC critical evaluation of the rotational-vibrational spectra of water vapor. Part I—Energy levels and transition wavenumbers

We report on >9W transverse-fundamental-mode CW output near 3 μm from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.

10-W-level diode-pumped compact 2.78 μm ZBLAN fiber laser

This is the second of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This article presents Preprint submitted to Journal of Quantitative Spectroscopy & Radiative Transfer10th June 2010 energy levels and line positions of the following singly deuterated isotopologues of water: HD16O, HD17O, and HD18O. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0–22 708, 0–1 674, and 0–12 105 cm−1 for HD16O, HD17O, and HD18O, respectively. For HD16O, 54 740 transitions were analyzed from 76 sources, the lines come from spectra recorded both at room temperature and from hot samples. These lines correspond to 36 690 distinct assignments and 8 818 energy levels. For HD17O, only 485 transitions could be analyzed from 3 sources; the lines correspond to 162 MARVEL energy levels. For HD18O, 8 729 transitions were analyzed from 11 sources and these lines correspond to 1 860 energy levels. The energy levels are checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators. This comparison shows that the measured transitions account for about 86 % of the anticipated absorbance of HD16O at 296 K and that the transitions predicted by the MARVEL energy levels account for essentially all the remaining absorbance. The extensive list of MARVEL lines and levels obtained are given in the Supplementary Material of this article, as well as in a distributed information system applied to water, W@DIS, where they can easily be retrieved. In addition, the transition and energy level information for H2 17O and H2 18O, given in the first paper of this series [J. Quant. Spectr. Rad. Transfer 110 (2009) 573-596], has been updated. Key words: Water vapor, transition wavenumbers, atmospheric physics, energy levels, MARVEL, information system, database, W@DIS, infrared spectra, microwave spectra, HD16O, HD17O, HD18O

/pdf/iupac-critical-evaluation-of-the-rotational-vibrational-553dhleh51.pdf

IUPAC Critical Evaluation of the Rotational-Vibrational Spectra of Water Vapor. Part II. Energy Levels and Transition Wavenumbers for HD16O, HD17O, and HD18O

Water-vapor lasers oscillate on more than a hundred pulsed lines and over a dozen CW lines over the wavelength range from 7 to 220 μ (1300-45 cm-1). Nearly eighty of these lines are now identified as vibrational-rotational and pure rotational transition in the low-lying vibrational states of the water-vapor molecule. The structure of the water-vapor molecule is reviewed, and the mechanisms responsible for creating population inversions in water-vapor discharges are discussed. It is shown how a model, based on perturbations between rotational levels of different vibrational states, can be used to explain the laser action and to predict new laser lines. Detailed summaries of data on all observed laser lines in H 2 O16, H 2 O18, and D 2 O16and their identifications are presented. Some of the lines are newly reported, and more accurate wavelength measurements have been made for many of the lines. The observation of predicted laser lines in H 2 O18is shown to be a strong confirmation of the perturbation model. The list of references contains a fairly complete bibliography of previous work on the water-vapor laser, and a representative bibliography of work on the energy-level structure of the water-vapor molecule.

The water-vapor laser

We have constructed and tested an optical multiplexer for use with multimode optical fibers. The device utilized a blazed plane reflection grating with a single GRIN‐rod lens, and was made from commercially available components. The wavelength spacing of the two channels was 27 nm, the insertion losses were ⩽2.4 dB, and the crosstalk was <−30 dB. Optimized versions of the device should be capable of providing at least four channels, with still lower insertion losses, in a rugged stable package 1–2 cm long by 2–4 mm in diameter.

W. Tomlinson

Papers

The water-vapor laser

Optical multiplexer for multimode fiber transmission systems

Optical multiplexer for multimode fiber transmission systems