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Showing papers on "Wavelength-division multiplexing published in 1990"


Journal ArticleDOI
TL;DR: Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented.
Abstract: The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented Discussed also are critical technologies that are essential to progress in this field >

1,382 citations


Journal ArticleDOI
Andrew R. Chraplyvy1
TL;DR: In this paper, the power limitations of light-wave systems were analyzed as a function of a number of wavelength-multiplexed channels and methods for scaling these results with changes in system parameters were presented.
Abstract: Optical nonlinearities in the context of lightwave systems limitations are described. The nature and severity of system degradation due to stimulated Raman scattering, carrier-induced phase noise, stimulated Brillouin scattering, and four-photon mixing are discussed. The system power limitations are plotted as a function of a number of wavelength-multiplexed channels. Methods for scaling these results with changes in system parameters are presented. >

787 citations


Journal ArticleDOI
TL;DR: Recent advances in fully integrated acoustically tuned optical filters (ATOFs) for use in wavelength-division multiplexing (WDM) are reviewed and experiments in parallel processing of wavelength channels are described.
Abstract: Recent advances in fully integrated acoustically tuned optical filters (ATOFs) for use in wavelength-division multiplexing (WDM) are reviewed. Experiments in parallel processing of wavelength channels are described. The ATOF uses the photoelastic effect induced by a surface acoustic wave (SAW) to flip the polarization state of a narrow phase-matched band of wavelengths. A unique feature of the ATOF is that many wavelengths can be simultaneously and independently processed, because the associated SAW beams can be superimposed with negligible interaction at the drive levels required for complete polarization conversion. This parallel processing capability has been used to select as many as five out of eight laser channels in an experiment in which each channel was tagged by a separate microwave subcarrier. Polarization-independent devices are also discussed. A polarization-diversity ATOF that decomposes an input beam into TE (horizontal) and TM (vertical) components, interchanges TE and TM roles for the resonant wavelength, and reroutes the filtered beam into a spatially distinct port is described. >

179 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of gain saturation and gain dispersion were studied numerically for the case in which a fundamental soliton is launched at the amplifier input, and the results showed that fiber amplifiers may be useful for simultaneous amplification and compression of weak optical pulses.
Abstract: Pulse amplification in erbium-doped fiber amplifiers is studied by considering a general model that includes both gain saturation and gain dispersion. The effects of gain dispersion are studied numerically for the case in which a fundamental soliton is launched at the amplifier input. The results show that fiber amplifiers may be useful for simultaneous amplification and compression of weak optical pulses. Under high-gain conditions the input pulse is found to split into a train of amplified subpulses whose width and repetition rate are governed by the gain bandwidth. The numerical results are in qualitative agreement with recent experiments. >

80 citations


Journal ArticleDOI
TL;DR: In this paper, three component concepts for use in high-density wavelength division multiplexed optical systems are described, and applications envisaged for these components include broadband overlay for subscriber access networks and ultrahigh-capacity packet switching for telecommunications or parallel processing computer applications.
Abstract: Three component concepts for use in high-density wavelength-division-multiplexed optical systems are described. The applications envisaged for these components include broadband overlay for subscriber access networks and ultrahigh-capacity packet switching for telecommunications or parallel processing computer applications. The components each use a dispersive optical grating and integrated array of optoelectronic transducers to form a component with precisely defined multiple operating wavelength channels. Multichannel laser transmitter and direct detection receiver components suitable for up to about 50 independent channels separated by 1-2 nm in the 1300- to 1600-nm-wavelength range are described. >

67 citations


Journal ArticleDOI
Emmanuel Desurvire1
TL;DR: In this paper, the erbium-doped fiber amplifier noise figure spectrum and its evolution under various pumping regimes were analyzed and it was shown that noise figures in the range + or 0.15 dB around the 3-dB quantum limit are possible within a spectral band of 50 nm.
Abstract: The erbium-doped fiber amplifier noise figure spectrum and its evolution under various pumping regimes is analyzed. The analysis shows that noise figures in the range +or-0.15 dB around the 3-dB quantum limit are possible within a spectral band of 50 nm. This demonstrates the possibility of quantum-limited amplification for broadband wavelength-division multiplexed (WDM) signals. >

56 citations


Journal ArticleDOI
Emmanuel Desurvire1
TL;DR: The possibility of quantum limited or near quantum limited noise regime for amplification of wavelength division multiplexed signals in erbium doped fiber amplifiers pumped near 980 and 1480 nm is demonstrated.
Abstract: A small signal analysis of the noise figure spectral distribution in erbium doped fiber amplifiers pumped near 980 and 1480 nm is presented. In the case where signal-spontaneous beat noise is the dominant cause of signal-to-noise ratio (SNR) degradation, it is shown that noise figures in the +/-0.2-dB range around the 3-dB quantum limit are possible within a spectral band of 50 nm, with the result applying to lambda(p) = 980-nm and lambda(p) = 1460-nm pump wavelengths. For lambda(p) > 1460 nm, a noise figure penalty of 0.5 to 1.2 dB above the quantum limit is found. This study thus demonstrates the possibility of quantum limited or near quantum limited noise regime for amplification of wavelength division multiplexed signals in erbium doped fibers.

54 citations


Journal ArticleDOI
TL;DR: In this paper, a monolithic integration of an antiresonant reflecting optical waveguide (ARROW)-type demultiplexer and photodetector is discussed, and the isolation was theoretically calculated to be -21.6 dB between the wavelengths of 0.78 and 0.88 mu m.
Abstract: A monolithic integration of an antiresonant reflecting optical waveguide (ARROW)-type demultiplexer and photodetector is discussed. The isolation was theoretically calculated to be -21.6 dB between the wavelengths of 0.78 and 0.88 mu m, with a maximum detecting efficiency of 58% in a short demultiplexing/photodetecting length of 100 mu m. The fundamental characteristic was demonstrated experimentally. This type of device can be applied to a wavelength division multiplexing (WDM) system with comparatively wide wavelength separation, e.g. 1.3- and 1.55- mu m wavelengths. >

49 citations


Proceedings ArticleDOI
03 Jun 1990
TL;DR: The proposed lightpath architecture trades the ample bandwidth obtained by using multiple wavelengths for a reduction in the number of processing stages and a simplification of each switching stage, leading to substantially increased throughput.
Abstract: An inherent problem of conventional point-to-point wide area network (WAN) architectures is that they cannot translate optical transmission bandwidth into comparable user-available throughput due to the limiting electronic processing speed of the switching nodes. A solution to wavelength division multiplexing (WDM)-based WAN networks that addresses this limitation is presented. The proposed lightpath architecture trades the ample bandwidth obtained by using multiple wavelengths for a reduction in the number of processing stages and a simplification of each switching stage, leading to substantially increased throughput. The principle of the lightpath architecture is the construction and use of a virtual topology network in the wavelength domain, embedded in the original network. A study is made of the embedding of virtual networks whose topologies are regular, using algorithms which provide bounds on the number of wavelengths, switch sizes, and average number of switching stages per packet transmission. >

48 citations


Patent
17 Apr 1990
TL;DR: In this article, a wavelength division multiplexing optical transmission system is disclosed which transmits light of wavelengths λ 1, λ 2 and λ 3 (λ 1 <λ 2 <λ 3) by way of a single optical fiber.
Abstract: A wavelength-division multiplexing optical transmission system is disclosed which transmits light of wavelengths λ1, λ2 and λ3 (λ1 <λ2 <λ3) by way of a single optical fiber. An optical multiplexer/demultiplexer of the filter type is used which includes a parallelogram prism, a first filter formed on a side face of the parallelogram prism, and second and third filters formed on the opposite side face of the parallelogram. Bidirectional optical fiber communications between the central telephone exchange side and a subscriber side can be achieved using such optical multiplexer/demultiplexer of the filter type. With the arrangement of the invention, an optical multiplexer/demultiplexer of the filter type can be produced at a low cost without the necessity of using a filter having a wide stopping band as a filter to be formed on a parallelogram prism.

47 citations


Proceedings ArticleDOI
03 Jun 1990
TL;DR: The multihop architecture, which provides a way of tapping the capacity potential available in lightwave networks, is described and solutions in which the traffic flows over a derived connectivity diagram such that the largest flow on any link is minimized are sought.
Abstract: The multihop architecture, which provides a way of tapping the capacity potential available in lightwave networks, is described. Within this architecture, each network node is equipped with some small number of transmitters and receivers, each of which can communicate on one wavelength. Transmitters and receivers are connected to an optical medium, which is physically configured in such a way that the entire spectrum of wavelengths in use is potentially accessible by each node. Then, an assignment of transmit and receive wavelengths to each node defines the logical connectivity among nodes. Furthermore, the use of optically agile transceivers (i.e. slowly tunable lasers or optical filters) permits the logical connectivity to be updated in response to changing traffic patterns and failure/recovery of nodal transmitters and receivers. The flow and wavelength assignment problem is studied. Solutions in which the traffic flows over a derived connectivity diagram such that the largest flow on any link is minimized are sought. Examples of the resulting connectivity diagram and traffic flow are presented for selected nonuniform point-to-point traffic matrices. >

Journal ArticleDOI
TL;DR: In this article, the relative gain differences among channels in WDM-amplified lightwave systems can be corrected in two-stage fiber amplifiers having complementary gain spectra in each stage.
Abstract: Relative gain differences among channels in WDM-amplified lightwave systems can be corrected in two-stage fiber amplifiers having complementary gain spectra in each stage. With two channels spaced by 2.5 nm, relative gain corrections of 1 dB were demonstrated. Simulations show that this method can be used to dynamically equalize the channel gain in long-distance transmission systems. >

Journal ArticleDOI
Shuji Suzuki1, M. Nishio1, Takahiro Numai1, M. Fujiwara1, M. Itoh1, S. Murata1, N. Shimosaka1 
TL;DR: In this article, a photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed, and the potential of 100 wavelength division channels in such switching systems is estimated, based on InP optical integrated circuits.
Abstract: A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. A switching system using wavelength switches and multistage switching networks is discussed. A crucial point in developing this switching system is to achieve a large number of wavelength-division channels. The potential of 100 wavelength-division channels in such switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization which permits the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift is proposed. An eight-channel wavelength-division switching experiment, using phase-shift-controlled distributed feedback laser diodes as tunable wavelength filters, is reported. >

Journal ArticleDOI
Fujiwara Masahiko1, N. Shimosaka1, Makoto Nishio1, S. Suzuki1, Shuntaro Yamazaki1, S. Murata1, K. Kaede1 
TL;DR: In this article, a coherent photonic wavelength-division (WD) switching system utilizing a coherent wavelength switch ( lambda switch) is proposed, where the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator.
Abstract: A coherent photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch ( lambda switch), is proposed. In the proposed coherent lambda switch, the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator. The coherent photonic WD switching system has the following features; (1) low crosstalk switching for dense WDM signal, and (2) large line capacity capability. Design considerations show that 32 wavelength division channels can be available with a coherent lambda switch. It is also shown that a broadband metropolitan-area-network with over 1000 line capacity is possible, using a multistage connection in the coherent lambda switches. The switching function of the coherent lambda switch is demonstrated in a two-channel wavelength-synchronized switching experiment, using 8-GHz-spaced, 280-Mb/s optical FSK signals. >

Journal ArticleDOI
TL;DR: In this paper, a rib waveguide-based multiplexer/demultiplexer based on GaInAsP/InP was realized for bidirectional optical communication systems.
Abstract: We have realized a novel wavelength division multiplexer/demultiplexer based on rib waveguides in GaInAsP/InP. The device is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant and has sinc2‐type characteristics. Our devices have center wavelengths around 1.3 μm, filter half‐widths 10–15 nm, and far end isolation down to −17 dB. The structure is suited for integration into optoelectronic integrated circuits for applications in bidirectional optical communication systems.

Journal ArticleDOI
TL;DR: Wavelength-selective characteristics in the AO module are established and the crosstalk from other wavelengths is found to be reduced by decreasing slightly the switching transfer efficiency.
Abstract: Optical integrated switching systems using collinear acoustooptic (AO) interactions for wavelength division multiplexing (WDM) systems are discussed. The AO switch module has excellent advantages compared to electrooptic switches. Optical WDM signals can be wavelength-selectively switched by frequency multiplexed surface acoustic waves. WDM switching systems are proposed as an application of this AO switch, and optical insertion loss, crosstalk, and optical frequency shift are discussed. Wavelength-selective characteristics in the AO module are established. The crosstalk from other wavelengths is found to be reduced by decreasing slightly the switching transfer efficiency. The wavelength-selective switching was experimentally demonstrated with a slab-type module of a 4-mm interaction region, where the WDM interval of 25.2 AA was realized. This wavelength interval can be decreased by increasing the interaction length. >

Journal ArticleDOI
TL;DR: Analyses of four broadband fiber-optic subscriber loop architectures indicate that splitter-based passive loops share electronics more effectively among subscribers than loop architectures requiring dedicated (per-subscriber) electronic interfaces, resulting in projected cost advantages for the splatter-based networks.
Abstract: Analyses of four broadband fiber-optic subscriber loop architectures, including active (high-speed time division multiplexing (TDM)-based) and passive (dense wavelength division multiplexing (WDM)-based, WDM-based with an analog subcarrier-multiplexing overlay, and splitter-based) double-star topologies, are presented. The analyses focus on specific demonstrated architectures and use component cost projections based on learning curves to estimate future network costs on a per-subscriber basis. Also investigated is the sensitivity of projected cost-per-subscriber to remote multiplexing node size and to double-star prove-in distance. The results indicate that the four architectures have very different double-star prove-in distances and that loop costs are minimized for much smaller remote node sizes than active loops, thus permitting cost-effective deployment of passive loops for smaller groups of subscribers. In addition, cost breakdowns for the four architectures indicate that splitter-based passive loops share electronics more effectively among subscribers than loop architectures requiring dedicated (per-subscriber) electronic interfaces, resulting in projected cost advantages for the splitter-based networks. >

Proceedings ArticleDOI
02 Dec 1990
TL;DR: Supervisory (SV) signal transmission techniques are proposed for transmission systems with inline optical amplifiers by modulating the pump light power of the optical amplifier with a 2 Mb/s bipolar signal, without degrading the line signal.
Abstract: Supervisory (SV) signal transmission techniques are proposed for transmission systems with inline optical amplifiers. Several methods of sending an SV signal over the same fiber along with the line signal passes are examined. Transmission over 75 km along with a 1.8 Gb/s line signal is confirmed by modulating the pump light power of the optical amplifier (laser diode) with a 2 Mb/s bipolar signal, without degrading the line signal. The remaining pump light unabsorbed by the amplifying fiber carries the SV signal. Another method described is polarization modulation of line-signal light. A transmission experiment over a 1000 km fiber through 14 optical amplifiers confirms the applicability of polarization modulation. >

Journal ArticleDOI
TL;DR: A four-channel wavelength-division-(de)multiplexing device, operating over optical wavelengths of 543.0 to 632.8 nm, has been successfully fabricated on newly developed locally sensitized polymer (photo-lime gelatin) microstructure waveguides (PMSW's).
Abstract: A four-channel wavelength-division-(de)multiplexing [WD(D)M] device, operating over optical wavelengths of 543.0 to 632.8 nm, has been successfully fabricated on newly developed locally sensitized polymer (photo-lime gelatin) microstructure waveguides (PMSW’s). The WD(D)M device exhibits a cross talk of less than −40 dB between adjacent channels and a diffraction efficiency of better than 50%. The angular and spectral bandwidths for the device are ~0.2–0.4° and ~4–10 nm, respectively. Such sensitivities can significantly increase the WD(D)M channel density for optical interconnect architectures. Since the PMSW device can be constructed on a variety of substrates, including insulators, semiconductors, conductors, and ceramics, the demultiplexing technique that we report is suitable for use in a variety of optical-computing, signal-processing, and communication applications.

Journal ArticleDOI
TL;DR: An all-fibre WDM broadcast network has been demonstrated, employing two stages of Er-doped fibre power amplifiers and fused-f fibre splitters, that is capable of distributing 12 wavelengths, each modulated at 2.2 Gbit/s, to 39 530 064 customers from a single head-end.
Abstract: An all-fibre WDM broadcast network has been demonstrated, employing two stages of Er-doped fibre power amplifiers and fused-fibre splitters, that is capable of distributing 12 wavelengths, each modulated at 2.2 Gbit/s, to 39530064 customers from a single head-end.

Patent
29 Aug 1990
TL;DR: In this paper, an optical frequency division multiplexing (OFDM) transmitter is described, which comprises a plurality of optical transmitters having different optical frequencies, an optical combiner multiplexer having optical signals outputted by the different transmitters, and an optical filter having passbands, each of which is approximately in accordance with the frequency of each of the signals.
Abstract: An optical frequency division multiplexing transmitter is disclosed, which comprises a plurality of optical transmitters having different optical frequencies; an optical combiner multiplexing optical signals outputted by the different optical transmitters; and an optical filter having passbands, the frequency of each of which is approximately in accordance with the frequency of each of the signals, in which the signal thus multiplexed is inputted.

Journal ArticleDOI
TL;DR: In this paper, the simultaneous amplification of 16 distributed feedback (DFB) lasers over a 34-nm spectral range in an erbium-doped fiber amplifier is reported, with a total of 100 studio-quality analog FM-TV channels and six 622-Mb/s channels.
Abstract: The simultaneous amplification of 16 distributed feedback (DFB) lasers over a 34-nm spectral range in an erbium-doped fiber amplifier is reported. Sixteen DFB lasers spaced at approximately 2-nm intervals and covering 34 nm in the 1.55- mu m band were modulated with a total of 100 studio-quality analog FM-TV channels and six 622-Mb/s channels. >

Journal ArticleDOI
Naoya Henmi1, Yasuhiro Aoki1, Sadao Fujita1, Y. Sunohara1, M. Shikada1 
TL;DR: In this article, the authors achieved -30.8 dBm (630 photon/bit) receiver sensitivity at 10 Gb/s, with an Er/sup 3+/-doped optical fiber preamplifier.
Abstract: The achievement of -30.8 dBm (630 photon/bit) receiver sensitivity at 10 Gb/s, with an Er/sup 3+/-doped optical fiber preamplifier, is discussed. This is an 8.3-dB sensitivity improvement over the avalanche-photodiode/FET receiver. Power penalties caused by a noise increase due to Rayleigh backscattering by the transmission optical fiber have been evaluated. Approximately -30-dB Rayleigh scattering from a 20-km optical fiber resulted in a 3.5-dB power penalty for a 25-dB-gain optical amplifier. >

Journal ArticleDOI
TL;DR: A point-to-point or single-ended communications technique based on single-mode optical fibers that uses all-optical pulse multiplexing at the transmitter and coherent optical correlation at the receiver shows potential for application to secure untappable communications, fiber local-area networks, and optical ranging in the presence of a strong white-light background.
Abstract: We propose a point-to-point or single-ended communications technique based on single-mode optical fibers that uses all-optical pulse multiplexing at the transmitter and coherent optical correlation at the receiver. This technique shows potential for application to secure untappable communications, fiber local-area networks, and optical ranging in the presence of a strong white-light background. The system can employ a low-coherence source, is insensitive to source phase noise and polarization-state rotation in the fiber link, and uses simple electronic threshold detection. Coherent correlation and anticorrelation are demonstrated experimentally, and practical requirements are examined.

Journal ArticleDOI
TL;DR: In this paper, a description of high-bit-rate fiber-optic non-coherent frequency-shift keying (FSK) transmission field experiments using Er/sup 3+/-doped optical amplifiers is given.
Abstract: A description is given of high-bit-rate fiber-optic noncoherent frequency-shift keying (FSK) transmission field experiments using Er/sup 3+/-doped optical amplifiers. Transmission distances of 70 km for a four-channel 6.8-Gb/s capacity experiment and 177 km for single-channel 1.7-Gb/s transmissions were demonstrated in a typical field environment. Measurements of receiver sensitivity dispersion penalty, interchannel crosstalk, and long-term bit-error-rate performance are presented. Results show negligible degradations due to >3000-ps/nm dispersion and interchannel crosstalk, in addition to stable long-term performance. This performance demonstrates the applicability of noncoherent FSK and fiber amplifier technologies. >

Patent
Klaus Panzer1, Thomas Neuhaus1
28 Sep 1990
TL;DR: In this paper, the authors proposed a bidirectional light waveguide telecommunication system with a passive light-waveguide bus network extending between a switching center and a plurality of subscriber locations, where only the switching center is designed for a normal bid-irectional wavelength division multiplex operation and is provided for this purpose with an electro-optical transmission element, an opto-electrical receiving element and an optical filter.
Abstract: In a bidirectional light waveguide telecommunication system having a passive light waveguide bus network extending between a switching center and a plurality of subscriber locations, only the switching center is designed for a normal bidirectional wavelength division multiplex operation and is provided for this purpose with an electro-optical transmission element, an opto-electrical receiving element and an optical filter, whereas only a combined opto-electrical receiving/electro-optical transmitting module that respectively works only in the time separation mode and is designed for emitting light having a wavelength for reception by the opto-electrical receiving element of the switching center is provided in the subscriber locations. In this combined receiving/transmitting module, the transmitting diode can be used, in alternation, as a receiving diode; alternatively thereto, the combined receiving/transmitting module can be formed with a laser module provided with a laser diode transmitted and with a monitor photodiode which is used, in alternation, as a receiving diode.

Proceedings ArticleDOI
TL;DR: In this article, the biconical taper process has been used for the development of a number of optical fiber components, such as polarizers, analyzers, and mode or wavelength filters.
Abstract: The rapid development and deployment of optical fiber for a variety of applications has resulted in a similarly rapid development of myriad components to effectively utilize the fiber. Thus, for example, significant work has been done over the past several years in the development of sources and detectors, connectors, and splices. These components share the common trait of being external to the fiber and hence not part of the fiber per se. Another class of components, however, is made from the fiber itself. A number of components, such as polarizers, analyzers, and mode or wavelength filters, require only simple bending of the fiber in a specified manner. On the other hand, such techniques as polishing, etching, and heating can also be used to alter the transmission properties of the fiber. While a number of interesting devices have been made by these procedures, the present paper is limited to devices made by the biconical taper process. If a fiber is heated and stretched, a biconical taper is f...

Journal ArticleDOI
TL;DR: The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology.
Abstract: The technical feasibility of a lightwave communication system capable of providing service to thousands of subscribers within cities or large suburban areas is examined. Each subscriber in this system has available upon demand an aggregate bit rate of up to 100 Mb/s. The aggregate bit rate of the entire network is on the order of 5 Tb/s. The network topology is that of a star-on-star wherein each subscriber line terminates on one of a multitude of remote concentrators. Each high-speed link from a remote concentrator to a centrally located time-multiplexing photonic switch consists of a single-mode fiber carrying several wavelength-division multiplexed (WDM) channels. Each channel operates in a time-division multiplexed (TDM) mode at a data rate of 2 Gb/s and is powered by a multimode laser. No regeneration is required at the central switch, and at the remote concentrators, each channel is terminated by a direct-detection receiver. The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology. >

Proceedings ArticleDOI
15 Feb 1990
TL;DR: In this paper, the gain dynamics of erbium-doped fiber amplifiers are studied both experimentally and theoretically, and it is shown that the transients associated with gain saturation and gain recovery during multichannel amplification have long characteristic times, i.e. in the 100 its-1 ms range.
Abstract: The gain dynamics of erbium-doped fiber amplifiers are studied both experimentally and theoretically. It is shown that the transients associated with gain saturation and gain recovery during multichannel amplification have long characteristic times, i.e. in the 100 its-1 ms range. Such slow gain dynamics effectively prevent saturation-induced crosstalk and intermodulation distortion effects in the amplification of high-speed WDM and FDM signals.

Patent
09 Apr 1990
TL;DR: In this article, a concave diffraction grating is used to form an aperture at which the interrogation signal will be formed, and a plurality of optical emitters are positioned such that the emitter output signal strikes the concave diffusion grating, and is focused onto the aperture, such that a portion of the emitters signal enters the aperture and forms one of the component signals.
Abstract: An optical source for use in an optical sensing system such as a wavelength division multiplexing system. The source produces an optical interrogation signal comprising a plurality of component signals, each component signal comprising light in a wavelength band different from the wavelength bands of the other component signals. The source comprises a concave diffraction grating, means for forming an aperture at which the interrogation signal will be formed, and a plurality of optical emitters. Each emitter is positioned such that the emitter output signal strikes the concave diffraction grating, and is focused onto the aperture, such that a portion of the emitter signal enters the aperture and forms one of the component signals. As a result, the component signal wavelengths are not sensitive to temperature-induced fluctuations in the emitter output signal.