Various methods, systems, and apparatuses are described in which a light source (101) capable of lasing is wavelength locked by an injected light signal. The light source (101) capable of lasing, such as a Fabry-Perot laser diode, may have antireflective coating on one or more facets of the light source (101) capable of lasing. The light source (101) capable of lasing receives a spectral slice of a light signal from a broadband light source (113) to wavelength lock the output wavelength of the light source (101) capable of lasing within the bandwidth of the injected light signal. A current pump (141) may bias the light source (101) capable of lasing to operate as a reflective regenerate semiconductor optical amplifier so that the injected light is reflected back out a front facet after being amplified and wavelength locked. The current pump (141) may also bias the light source (101) capable of lasing such that the externally injected narrow-band light signal into the light source (101) capable of lasing suppresses the lasing modes outside of the bandwidth of injected incoherent light.

A light source cable of lasing that is wavelength locked by an injected light signal

Multi-wavelength light having a frequency band equal to or greater than the FSR of an AWG is demultiplexed into individual wavelength channels, and power level deviations between wavelength channels are suppressed An optical demultiplexer includes a wavelength-group demultiplexer that demultiplexes multi-wavelength light into wavelength groups formed from wavelength channels, and channel demultiplexers that demultiplex each wavelength group into wavelength channels light An optical multiplexer includes channel multiplexers that multiplex modulated signal light of each wavelength channel for each wavelength group, and a wavelength-group multiplexer that multiplexes, for each wavelength group, WDM signal light output from the channel multiplexers The FSR of the wavelength-group multiplexer/demultiplexer is set to be equal to or greater than the frequency band of the multi-wavelength light The channel multiplexer/demultiplexer is an AWG in which the FSR is approximately the full width at half maximum of the transmission characteristics of each port of the wavelength-group multiplexer/demultiplexer

Multi-wavelength optical modulation circuit and wavelength-division multiplexed optical signal transmitter

A method to obtain polarization characteristics of an optical transmission medium is disclosed. Sequentially plural different states of polarized light are launched into the optical transmission medium. Intensities of light emerging from the optical transmission medium through combinations of optical elements are measured to obtain Stokes parameters from which Stokes vectors describing the emerging light corresponding to each of the plural sequentially launched states of polarization are obtained; for at least three different launched states of polarization, descriptors are used of these launched states of polarization and the Stokes vectors describing the corresponding emerging light to calculate a Jones matrix which mathematically models the changes that the launched light when described in terms of a Jones vector is subject to when passing through the optical transmission medium; and, the Jones matrix is used to describe the polarization characteristics of the optical transmission medium.

Method and apparatus for measuring the polarization characteristics of optical transmission medium

The present invention discloses a method of configuring subnodes, or configuring a system of subnodes, in an optical network ring against both node and fiber failure by means of OADM, Optical Add Drop Multiplexer. The network comprises a working ring and a stand-by ring and each subnode includes selective optical filter means, optical 2x2 switch means and optical amplifier means. The method and the system is further comprising the steps of monitoring the inputs and outputs of each subnode at the working and stand-by rings by means of monitor device means, which are generating alarm signals upon detection of signal loss at a subnode. As a response to the alarm signal the state of the subnode, which causes the alarm signal, is transferred from a first state into one of a number of possible conditions as a function of the generated alarm signal, and thereby selecting a switch configuration for the subnode according to the new state to clear the error detected.

Optical add drop multiplex (oadm)

An OPC generates a pump light having the wavelength λs with a power larger than a threshold for generating a nonlinear effect in an optical fiber for a main signal having the wavelengths λ1 through λ4 transmitted from an OS, and wavelength-multiplexes the generated light with the main signal. When the pump light induces a nonlinear effect, a signal light having the wavelengths λ1′ through λ4′ is generated symmetrically to a main signal having the wavelength λ1 through λ4 about the pump light on a wavelength axis. Thus, in a wavelength multiplexing system designed based on an eight-wave transmission, a signal light can function as a compensation light even when only four waves are used at the initialization of the system, thereby compensating for the characteristics of the system operations. Furthermore, the system is effective in cost because it simply requires an OPC for generating a pump light regardless of the number of compensation lights to be generated.

Optical communications terminal station, optical signal transmission method, and optical signal increasing method in wavelength multiplexing system

PURPOSE:To provide the group delay optical equalizing circuit which can make the optical transmission line of an optical transmission system extremely fast and increase communication capacity by making amplitude characteristics constant irrespective of the frequency and widening the width of a band where linear group delay dispersion can precisely be compensated, and thus increasing the degree of freedom of designing. CONSTITUTION:This group delay optical equalizing circuit is equipped with an optical amplifier 15 which is constituted by forming a low-reflection film at one light incidence/projection end of an optical amplifying medium and a high-reflection film at the other light incidence/projection end, gives specific group delay dispersion characteristics by making incident light from the low-reflection film side travel reciprocally between the low-reflection film and high-reflection film and amplifies and emits the light from the low-reflection film side and an optical path control means which guides the transmitted light to this optical amplifier 15 and guides the projection light from the optical amplifier 15 to optical fibers 11 and 16 used for the optical transmission line; and the group delay dispersion characteristics of the optical amplifier 15 are set reverse to linear group delay dispersion characteristics that the optical fibers 11 and 16 of the optical transmission line have.

Group delay optical equalizing circuit

PROBLEM TO BE SOLVED: To suppress intense noise, to transmit a signal with narrow ASE (amplified natural discharge light) at a higher bit rate and to effectively use an optical band. SOLUTION: The natural discharge light of a wide band is emitted from a light source 21 and an optical filter 22 cuts specified wavelength light and inputs it in an optical modulator 23. A part of wavelength obtained in the optical filter 22 is extracted by an optical coupler 24 and a photodiode 25 measures the light intensity amplitude. The measured result is polarity-inverted in an inversion amplifier 27 and it is set to be the modulation input of an optical modulator 23. Thus, an ALC processing (automatic level control) is executed, the light intensity fluctuation of wavelength light is suppressed and an optical carrier is generated. The optical carrier is inputted to an optical modulator 26 and is modulated with data D inputted through an amplifier 28. Thus, an optical transmission signal is obtained. Thus, the intense noise of the optical carrier can be suppressed by ALC and the signal of the high bit rate can be transmitted with the considerably low bit error rate.

Light transmitter and light transmission system

PURPOSE:To insert an optical signal of an optional wavelength from a 1st stage and to extract a desired optical signal among plural optical signals at a final stage at a low cost and low loss by providing proper delay and phase shift to optical transmission lines in plural optical distributers connected in series each having a couple of input terminal and output terminal CONSTITUTION:Optical distributers each having optical input and output terminal in pairs are connected in series by using an optical guide path to form a coherent optical transversal filter A couple of optical guide paths between the optical distributers are adjusted to have the same delay based on the length and the phase is shifted based on the optical signal wavelength Then a delay time T and a phase shift theta1-n-1 are set by a predetermined equation together with distribution ratio of the optical distributers C1-Cn by using optical delay lines D1-n-1 Then optical signals lambda1, 2-lambdad1, 2- An are inputted to one of the distributer C1 and optical signals lambdaa1, 2- are inputted to the other Thus, the optical signals lambdad1, 2- are extracted from the distributer Cn and the signals lambdaa1,2- are inserted at a low cost and low loss

Optical add drop wavelength multiplexer demultiplexer

PURPOSE:To measure the amplitude dispersion characteristics and the group delay time characteristics of an optical circuit at a wide frequency band by comparing the modulation components between a light to be measured and a reference light for obtaining the amplitude ratio and the phase difference and then displaying the amplitude/phase result by sweeping the frequency of a light source at a certain period CONSTITUTION:The output light of a DFB laser 1 is maintained to be a constant light intensity by an auto power control(APC) circuit 2 and is subjected to modulation by a sinusoidal wave by a light modulator 9 The modulation light is branched 12 into a reference light and a light to be measured and is subjected to photoelectric conversion 13 and 15 and then is fed to an amplitude/phase comparator 16, thus obtaining the amplitude ratio and the phase difference of sinusoidal wave signal components of a modulation frequency fm On the other hand, the light frequency of the DFB laser 1 is swept in triangular shape by temperature control of a Peltier element 4, a synchronization signal is sent from a multi-functional oscillator 5 to a display 17, and the amplitude ratio and the phase difference are displayed in time series based on the synchronization signal, thus measuring the amplitude dispersion characteristics and the group delay time dispersion characteristics of a light measurement circuit device 14 to be measured

Optical network analyzer

PURPOSE:To provide a variable light delay circuit capable of arbitrarily delaying transmission light and contributing the synchronous processing of an optical signal, in its turn the realization of an optical ATM exchange. CONSTITUTION:Plural primary group delay distributed light circuits 11 and 12 whose distributed codes differ and which are mutually connected in serial and a center light frequency control means 13 which variably controls the center light frequencies of the respective primary group delay distributed light circuits 11 and 12 are provided. The circuit is controlled in such a way that the sum of the group delay distribution of the respective primary group delay distributed light circuits 11 and 12 becomes zero distribution through the center light frequency control means 13.

Manitsushiyu Shiyaama

Papers

Group delay optical equalizing circuit

Light transmitter and light transmission system

Optical add drop wavelength multiplexer demultiplexer

Optical network analyzer

Variable light delay circuit