WO2003036826A1 - Spectrometre - Google Patents

Spectrometre Download PDF

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Publication number
WO2003036826A1
WO2003036826A1 PCT/EP2002/011840 EP0211840W WO03036826A1 WO 2003036826 A1 WO2003036826 A1 WO 2003036826A1 EP 0211840 W EP0211840 W EP 0211840W WO 03036826 A1 WO03036826 A1 WO 03036826A1
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WO
WIPO (PCT)
Prior art keywords
module
monitoring
spectrometer
optical signal
spectrometer module
Prior art date
Application number
PCT/EP2002/011840
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English (en)
Inventor
Bengt-Erik Olsson
Magnus Karlsson
Henrik Sunnerud
Original Assignee
Pro Forma Alfa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP01125128A external-priority patent/EP1306987A1/fr
Application filed by Pro Forma Alfa filed Critical Pro Forma Alfa
Publication of WO2003036826A1 publication Critical patent/WO2003036826A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07955—Monitoring or measuring power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal

Definitions

  • This invention relates to a spectrometier module, a monitor module, a monitoring unit and a monitoring system for use in monitoring an optical network.
  • the invention further relates to a spectrometer device, for spectrometry purposes.
  • optical signals for purposes as carrier of information and the like is currently increasing rapidly. Consequently, there is a current heed for developing new methods and products for dealing with this kind of information.
  • fibre optical communication systems that are used for transferring large amount of information over large distances.
  • Such system comprise a plurality of different network elements, being interconnected to form a communication network.
  • these networks are becoming larger and larger, and including more and more soohisticated network components, the risk for network faults is increasing rapidly. Consequently, there is a need for surveillance systems, keeping track of the optical signals being transmitted in the network, and reporting when an error has occurred.
  • the proposed means of monitoring the s'ignal quality in WDM systems are usually limited to monitoring of the signal power as a function of wavelength, by use of some spectrometer technology, such as e.g. fibre Bragg gratings, such as for example described in the patent document WO 0102885.
  • This spectrometer technology suffers from the same drawbacks as the ones listed above.
  • An alternative monitoring method is further described in "Quality monitoring of optical signals influenced by chromatic dispersion in a transmission fibre using averaged Q-factor evaluation" by I. Shake, H. Takahara, K. Uchiyama, and Y. Yamabayashi, IEEE Photonics Technology Letters, vol 13, pp385-387
  • an object of this invention is to achieve a spectrometer module, a monitor module, a monitoring unit and a monitoring system for use in monitoring an optical network, overcoming the above- mentioned drawbacks with the prior art.
  • a further object s to achieve a way of measuring properties of an optical signal, such as power, state of polarisation and degree of polarisation verjsus wavelength in an efficient way. Yet a further object is to achieve a spectrometry device, overcoming the drawbacks with the prior art.
  • a spectrometer module comprising:
  • -an input for receiving an incoming optical signal
  • -a variable differential group delay (DGD) jelement for applying a variable birefringence retardation to said incoming optical signal
  • -a detector unit for detecting the power of a defined state of polarisation of a signal exiting s ( Iaid variabIl'e
  • variable DGD element in a spectrometer module, it is possible to perform measurements on an incoming optical light signal, for detecting parameters such as polarization state and degree of polarisation as a function of the wavelength of the incoming signal.
  • said variable DGD element is implemented spatially.
  • said variable DGD element comprises a plurality of laterally spaced sub-elements having different optical lengths, whereby different parts of the incoming optical signal is arranged to be transmitted through different sub-elements of the DGD element.
  • said incoming optical signal is arranged to have essentially the same width as said variable DGD element, thereby covering each! of said laterally spaced sub elements.
  • said DGD element is optimally used.
  • said variable DGD element suitably comprises a plane incidence surface, being essentially orthogonal to the optical signa. path, and a stepped exit surface.
  • variable DGD element may comprise a birefringent element having a decreasing thickness in a direction being transverse to said incoming optical signal. Thereby different parts of the optical signal beam experiences different optical paths.
  • said incoming optical signal is suitably arranged to be slightly divergent.
  • said variable DGD element is implemented temporally, by use of an electrical control signal that chjanges the DGD with time.
  • said variable DGD eliement is comprised by a birefringent system, being essentially sandwiched between a first and a second reflective element, whereby said incoming optical signal is arranged to be reflected between said reflective elements ⁇ one or more times before outputted from said birefringe'nt system.
  • said first and second reflective elements are constituted by a first and second mirror element, respec- tively.
  • said first and second reflective elements are constituted by a first and a second retrore- flector, respectively.
  • the same birefringent element may iby utilized many times .
  • a polarizer is arranged between said variable DGD element and said detector unit, said polarizer not being aligned relative to the birefringence eigenaxes of said DGD ele- ment .
  • said incoming optical signal preferably has a polarisation so as to inject light in] both birefringence eigenaxes of said variable DGD el ⁇ ment .
  • variable DGD element is manufac- , tured from an electro-optical birefringent material.
  • said variable DGD element is suitably arranged between a first and a second electrode, said electrodes being arranged to generate an electric field over said variable DGD element.
  • a variable DGD element is achieved, being easy to control by means of an electronic control unit or the like.
  • sajid variable DGD element may be connectable with an acuslto-optic transducer, for achieving the above controllability.
  • said detector unit is preferably connectable with an electronic processing device, in which a detected signal may be processed to extract information regarding properties such as power, state o'f polarisation and degree of polarisation of said incoming optical signal as a function of wavelength.
  • a spectrometer device for measuring the optical spectrum of an optical signal, characterised in that said spectrometer device comprises a first and a second spectrometer module as described in above, and a polarisation splitter, whereby said polari- sation splitter is arranged to split said optical signal into a first and a second signal segments, whereby said first signal segment is arranged to be inputted to said first spectrometer module, and said second
  • the inventive spectrometer module may be used for pure spectrometry, analysing partly or arbitrary polarised light.
  • Such a device may for example be used in .1 the fields of chemistry, process industry, astronomy or pharmaceutical industry, or in any other field in which spectrometry is applied.
  • a monitor module for measuring properties such as power, state of polarisation and degree of polarisation of an incoming optical signal as a function of wavelength
  • said monitor module comprising: -a polarisation control module being connected with a control unit,
  • said polarisation control module comprises: - a first birefringent element,
  • each of said birefringent elements being connected with a power source for individual control of the birefringence
  • the birefringent eigenaxes of said second birefringent elemejnt is rotated by 45 degrees in relation to the birefringept eigenaxes of said first birefringent element.
  • the birefringent eigenaxes of said first and second birefrin- i gent elements are coinciding, and a quarter wave element, being rotated by 45 degrees in relation to the birefringent eigenaxes of said birefringent elements, is arranged between said first and second birefringent [elements.
  • a unit for monitoring an optical signal being transmitted in an optical network
  • said unit comprising : -a coupler, being arranged to be inserted along a optical transmission path of said optical network, said coupler having a main in- and output, respectively, j for receiving and transmitting said optical signal and at! least one drop output, to which a portion of said optical signal is droppable, said drop output being connected! with one of a spectrometer module as described above and a monitor mod- ule as described above.
  • a monitoring unit may be, installed in an optical network, in a position which is de- sired to monitor.
  • a monitoring system for an optical network comprising a plurality of network elements, such as transmitters, receivers, transmission lines, amplifi- ers or the like, said monitoring system comprising:
  • each of sjaid monitoring stations being positioned between two netwojrk elements of said optical network and each of said stations comprising one of a spectrometer module as described above, a moni- tor module above and a monitoring unit as described above and
  • monitoring hub being connected with eaqh monitoring station, said hub being arranged to receive measured sig- • nal data from each of said monitoring stations, and said monitoring hub comprising a processing unit' for processing said measured signal data.
  • a monitoring system for an optical network comprising a plurality of network elements,! such as transmitters, receivers, transmission line ⁇ , amplifiers or the like, said monitoring system comprising: -two or more monitoring stations, each of said monitoring stations being positioned between two network elements of said optical network, each of said stations being ar- i ranged to measure power, state of polarisation and degree of polarisation of an optical signal entering said monitoring station via said network, -a monitoring hub, being connected with each monitoring station, said hub being arranged to receive ⁇ measured signal data from each of said monitoring stations, and said monitoring hub comprising a processing unit for process- ing said measured signal data.
  • the invention may be used forj gaining information regarding the function of an entire network, for example enabling quick location of faults.
  • the above monitoring system as well as' the above monitoring module may be used for monitoring signal data quality in a wavelength division multiplexecl (WDM) fibre optical communication system.
  • the spectrometer module above may be used as a standalone spectrometer device, as stated above.
  • the above objects are wholly or partly , achieved by a method of monitoring and meas ⁇ ring properties such as power, state of polarisation and degree of polarisation of an incoming optical signal as a function of wavelength, the method comprising the stjeps of: -inputting said incoming optical signal to ' ⁇ variable DGD element, I
  • variable DGD element -applying a variable birefringence retardation to said incoming optical signal by letting it pass isaid variable DGD element, and -detecting the power of the signal exiting said variable
  • the DGD element having a determined state of polarisation.
  • said variable DGD element is comprised in a spectrometer module as described above.
  • the method suitably comprises the step of dropping said ' incoming optical signal from a wavelength division multiplexed (WDM) fibre optical communication system that is to be monitored.
  • WDM wavelength division multiplexed
  • FIG 1 is a schematic drawing of a firstj embodiment of the inventive spectrometer module.
  • Fig 2 is an alternative embodiment of t e construction as shown in fig 1, being independent upon the polarisation of the incoming optical signal.
  • Fig 3 is a schematic drawing of a second embodiment of the inventive spectrometer module.
  • Fig 4 is yet another schematic drawing jof a third embodiment of the inventive spectrometer mojdule showing only a spectrometer section of said module.'
  • Fig 5 is a schematic drawing of a fourth, embodiment of the inventive spectrometer module showing only a spectrometer section of said module.
  • Fig 6 is a schematic drawing of a fifth embodiment of the inventive spectrometer module showing only a spectrometer section of said module.
  • Fig 7 is a schematic drawing of a monitjor module, comprising a spectrometer module as shown i
  • Fig 8a and 8b is a schematic view showing two implementations of a polarisation control module, for use ⁇ in a monitor module as shown in fig 7. ⁇ '
  • Fig 9 shows a monitoring unit for insertion in an optical communication system, said monitoring unit comprising a monitoring module as shown in 'fig 7.
  • Fig 10 is a schematic drawing of an optical communication network, in which a plurality of monitoring units as shown in fig 9 is used for monitoring optical signal transmission in said network.
  • the spectrometer module comprises a variable DGD
  • This embodiment also comprises a polarizer 12, bejing ⁇ arranged between said variable DGD element 'll and said detector unit 13 and being non-aligned with the birefringent axes of the DGD element .
  • An incoming light signal 14, having a determined, well-defined state of polarisation may be inputted to said variable DGD element 11, having birefringent eigenaxes .
  • the variable DGD element 11 having birefringent eigenaxes .
  • I DGD element is electrically variable, meaning that an electric field may be applied over said DGD 1 eement 11, in order to change the birefrinence of said variable DGD element 11.
  • the variable DGD element is arranged between a first and second electrode (not shown) being connected with an electronic control unit.
  • an acoustic- optical transducer (not shown) may be connected with said variable DGD element 11 in order to change the birefringence of the DGD element 11 by applying an acoustic- optical transducer
  • the experienced birefringence j may be varied by for example applying an electrical field] over the variable DGD element 11.
  • the optical signal is arranged to pass said polarizer 12, whereafter the power of said optical signal is detected by meansj of said detector unit 13.
  • the power spectrum of the incoming optical signal 14 may be deduced by putting the variable DGD element in a plurality of birefringence' states, by for example applying different electrical fields to the DGD element, and measuring the corresponding detector power level for each birefringence state .
  • T he purpose of the spectrometer module is to extract the wavelength spectrum of the incoming optical signal 14, i.e. to obtain the power level at the various optical wavelengths.
  • a variable birefrin'gence retardation is applied to the signal.
  • the pplarization state of a signal after passing such an element will vary periodically with the optical frequency, wi ( th a period given by l/DGD where DGD is the differential group delay of the element.
  • the DGD in the birefringent element is electrically tunable, a tunable optical transfer function is achieved. After passing the polarizer, the wavelength components of the optical signal will attenuate differently, depending on what DGD has been applied. Consequently, the signal reaching the detector unit will be dependant upon the wavelength contents of the signal as well as upon the applied DGD. Thus, by measuring the
  • a second embodiment of the invention is shown in fig 3.
  • an incoming, polarized, slightly diverging optical signal beam 114 is arranged to 'hit a birefringent element 111, which has continuously decreasing thickness (and thereby differential group delay) in one transverse direction (denoted x in the fig ⁇ re) related to the signal path.
  • the polarization state after such a birefringent element 111 will continuously change spatially in the x-direction, with a rotation rate determined by the wavelength of the signal.
  • this spatial polarization rotation will be transformed to a point in a Fourier (focal) plane 117 of the lens 112, where the signal hits a detector array 113.
  • Each de-. c -. or of this array 113 will then measure the power of a pertain wavelength of the signal.
  • an 1 electrically controlled DGD as in the above described first embodiment is not necessary, but one uses a detector array to separate the wavelengths spatially.
  • FIG. 4 A detail of a third embodiment of the invention is shown in fig 4, showing only the DGD element.
  • This fig shows an embodiment in which variable DGD is implemented spatially.
  • an incoming optical signal' beam 214 is sufficiently wide so that it fills the entire width of a birefringent crystal 211, constituting a vajnable DGD " element .
  • the incoming optical signajl is polarized at an angle of 45 degrees in relation to thje polarization axis of the DGD element 211.
  • This element is electro-
  • the DGD element 211 is laterally divided into sub-elements of different length so that the beam feels different differential group delays over its different parts.
  • the signal is arranged to hit a polarizer (not shown) as [in fig 1, oriented at 45 degrees with respect to the birefringent eigenaxes of the DGD element (7.2) .
  • the optical signal beam is arranged to be detected by a detector as in fig 1.
  • a fourth embodiment of a DGD element for use in a spectrometer module according to the invention is shown in fig 5.
  • a voltage controls the differential group delay of a birefringent element directly.
  • An efficient way of doing this is to use a multipass structure, in which the light passes the same birefringent system sev- eral times.
  • an incoming optical light signal 314 having a well-defined state of polarization, is arranged to bounce back and forth between a first and a second mirror 3J12, 313 with a slightly tilted beam propagation direction,! so that the beam 314 hits a birefringent system 311, being arranged between said mirrors 312,313, several times.
  • one birefjringent element is electrically controlled by means of; an electrical control unit.
  • an electrical control unit By electrically altering the birefringence of this electrically controlled element, the net bire- fringence of the multipass structure as a whole will be altered, and thereby an electrically controllable DGD element has been realized.
  • the maximum amount of DGD that can be achieved in this manner will be the 'equal to the DGD of the birefringent system 311 times the number of passes through this system 311.
  • This kind pf multipass structure may replace the DGD element 11 in a structure as shown in fig 1.
  • a fifth embodiment of a DGD element for use in a spectrometer module according to the invention is shown in fig 6.
  • This embodiment shows an implementation of ⁇ a multi-pass structure, using retroreflectors . It is functionally similar with the embodiment shown in fig 5.
  • a incoming optical light signal 414 is reflected between a first and a second retroreflector 412,413 of slightly different size, also having a small dealignment ⁇ as shown in the fig 6. This enables a spi- raling light path as shown in fig 6.
  • an birefringent system 411 is ' arranged.
  • the optical light signal hits the birefringent system 411, being electrically controlled by means of an electronic control unit 415, and finally the light signal leaves the system through for example a flat polished corner 416 of said first retroreflector 412.
  • the light may also be arranged to leave the retroreflector by means of a bore or the like (not shown) .
  • the light beam 417 After leaving the birefringent multi- pass system 411 the light beam 417 will have exhibited a variable DGD that can be controlled by one or several applied voltages from said electronic control ⁇ unit 415.
  • the birefringent system 411 may comprise an arbitrary set of birefringent and electrically controlled elements in any orientations, but it must contain a minimum 1 of one birefringent element that has a differential group delay and one birefringent element that is electrically controlled. By electrically altering the birefringence of this controllable birefringent element, the net birefringence of the multipass structure as a whole may be altered, and an electrically controllable DGD have been realized. The maximum amount of DGD that can be achieved in this manner will be the equal to the DGD of the birefringent system 411 times the number of passes through this] system.
  • a spectrometer module as shown m fig 1, is used to generate a spectrometer device, 'for use as a standalone system for spectrometry.
  • a spectrometer device is independent of the polarization of the incoming light. This may be achieved by using a polarization diversity scheme as shown in Fig- ure 2 .
  • an incoming optical light signal 514 is spl it into its two orthogonal polari zation [components by a polari zation beam splitter 516 , and then .entering bire- fringent DGD elements 511 and 517, respectively, in which the birefringence (and hence DGD) are electronically controlled as described with reference to fig 1.
  • the exact realization of those elements 511, 517 is a;s described with reference to fig 1.
  • the light is transmitted through polarizers 512,518 respectively, which should be non-aligned with the birefringence eigenaxes of the re- spective variable DGD element 511, 517.
  • each branch of the spectrometer device correspond to a spectrometer module ⁇ as shown in fig 1. This spectrometry device allows spectrum analysis of an unpolarised incoming light signal.
  • a corresponding spectrometry device may also be achieved by utilizing spectrometer modules of any of the embodiments described above and showed in the drawings.' It may also be possible to combine two different embodiments in one spectrometry device, one embodiment for each branch, 511- 513 and 517-519, respectively.
  • a spectrometer device as described with reference to fig 5 is for example usable in the fields of process industry, chemistry, laboratory activity and pharmaceutical industry.
  • a spectrometer module 1 as described above with reference to fig 1, 3, 4, 5 or 6 may be comprised in a monitor module 2, as shown in fig 7.
  • the purpose of the monitor module 2 is to provide a system that isj able to measure power, state of polarization and degree of polari'za- tion of an incoming optical signal 4 as a function of wavelength, and in a preferred embodiment tihe general layout of a monitor module is shown in figure 7.
  • the sys- tern basically comprises a spectrometer module 1, as described above and a polarization control module 5, as will be closer described above. Further, a polariser 3 is arranged between said polariser control module 5 and said spectrometer module 1.
  • An incoming light signal 4 falls at the polarization control module 5, in which the polarization state of the incoming light signal 4 may be controlled electronically, as will be described below.
  • a polariser 3 t.hat only al- lows transmission of one polarization state!, and consequently the power of the light emanating from said polariser 3 will vary with the settings of the polarization control module.
  • the power of the light emanating from said polariser 3 will thereafter be detected by the spec- trometer module 1, as described above. Since the above spectrometer modules 1 are capable of separating different optical wavelengths, it is possible to detect the effect of different wavelength components within the light signal 4. Thereby, it is possible to measure the effect as well as the state of polarization as a function of wavelength of the incoming signal .
  • the polarization control section is driven by an electric signal from an electronic polarization control unit 7 which changes the polarization state of the incom- ing light 4 in a controlled manner.
  • the spectrometer module 1 detects the light and determines the power level of the various wavelength components of the signal, and does so for a number of settings of the polarization controller module 5. This will produce the required data, that may be outputted to an electronic processing unit 6. Further the spectrometer module utilizes an electrical control signal from an electronic control unit 15, as described above, to obtain the spectrum.
  • the 'detection process in the spectrometer module 1 must then be syn- chronized with the applied control signals from the electronic polarization control unit 7 in order to extract the desired information from the detected signal 4.
  • An alternative operation scheme drives the polarization control module 5 and the spectrometer module 1
  • the incoming light 4 hits a first and a second electrically controlled polarization waveplate 5a, 5b in sequence, said waveplates 5a, 5b being connected with said electronic polarization control unit 7.
  • the waveplates 5a, 5b can be either oriented so that their birefringence axis does not line up, as shown in figure 8a, or have aligned birefringence] axis but with a quarter-wave retarder 5c being arranged between said waveplate 5a, 5b with dealigned axes as shown in figure 5b.
  • Examples of physical implementation of the waveplates 5a, 5b can be electro-optic crystals (in integrated, bulk optics, or liquid crystal fashion) , electromechanical fi- ber squeezers, electromagnetically controlled Faraday rotators, or other schemes as described e.g. in the paper "Polarization-State Control Schemes for Homodyne and Heterodyne Optical Fiber Communications" by T .j Okoshi, IEEE i J. of Lightwave Technology, pp. 1232-1237, ivol . LT-3, 1985, which is hereby incorporated herein by reference.
  • the waveplates 5a, 5b change the polarization state of the signal 4 in a controlled manner, and measurement of the power level after a polarizer will enable the state of polarization to be determined.
  • larization control section 5 as shown in fig 8a will hereinafter described.
  • the optical signal 4 to be detected falls into a birefringent waveplate i5a, changing ⁇ the exit polarization state of the signal 4 as a function' of an applied voltage VI,
  • the birefringent >axes of the waveplates, representing states of polarization that may pass the waveplate unaltered, are shown with arrows in fig 8a-b. Consequently the birefringent axes of the first and second waveplates 5a, 5b are arranged with an angle of 45 degrees in relation to each other, so' that light entering the first waveplate 5a along its birefringent axes may be controlled by the second waveplate 5b, having an variable applied voltage V2.
  • quarter- wave plate 5c is arranged to provide the same effect, although the axes of the waveplates coincide.' It shall be noted that the above described polarization; control module may be used with any spectrometer module, not only ' the ones being described above.
  • a monitor module 2 as described above, ⁇ and as shown in fig 7, may be incorporated in a monitoring unit 20.
  • the monitoring unit 20 comprises an optical four-way directional coupler 21 that ⁇ s connectable with a first and a second transmission line 22, 23 for an optical signal S.
  • a small portion generally about 1%, ma'y be dropped from the transmission line to a monitor module 2, being connected with one port of said directional coupler 21. This small portion constitutes the incoming light signal 4, falling into the monitor module 2, as described above.
  • reflected light ' from the transmission line 22,23 may be detected as well, by positioning a detector 24 in a backward iport of the coupler 21, as shown in fig 9.
  • a further monitor module may be positioned in said backward port, instead of said detector (embodiment not shown) .
  • An optical network consists of a mesh-like structure of network elements 30 being any transmission or signal manipulation component within the network, 'such as transmitters, receivers, transmission lines or fibers, disper- sion compensating fibers, amplifiers, repeaters, regenerators, wavelength converters or optical cross-connects. Since the transmission of the optical signals through a network depend on a lot of the status of different net- work elements, it is valuable to known when network elements fail, and how such failures affect the optical signal . Thereby, the inventive monitoring system comprises a plurality of monitoring stations 31, being placed in various positions in said network.
  • the monitoring sta- tions each comprises a monitoring unit as showed in fig 9, but may also be constituted by any other construction utilizing a monitor module 2 as described above.
  • Each of said monitoring stations 31 is further connected to a central monitoring hub 32, receiving measured signal data from a plurality of monitoring stations 31, ⁇ being deployed within said network.
  • An example of such a system including monitor stations is shown in Fig 10.
  • the monitor stations 31, each comprising a monitoring module 2 are deployed between each network element 30.
  • Each monitoring module 2 is able to measure basic parameters as function of wavelength as described above.
  • wavelength-division multiplexed optical network it is possible to measure wavelength-division multiplexed data at the signal position, such ' as power, state of polarization and degree of polariz'ation.
  • the measured data from each monitoring module 2 is transmitted to a central monitoring hub 32 in which all monitored data of the transmission link is gathered.
  • Said monitoring hub 32 further comprises a processing unit and an in- formation display unit (not shown) .
  • the monitoring hub 32 Given the input from the monitor modules 2 via the monitoring stations 32, the monitoring hub 32 will be able to
  • the monitoring system is above described with reference to a wavelength-division multiplexed optical commu- i nication network.
  • the monitoring system may be used with any communication system in which] the above- i , mentioned measured parameters are of interest.
  • the spectrometer module as described above may be implemented in other ways than the ones described above, without departing from the scope and spirit of this invention, as described by the appended claims.
  • spectrometer module are not only useful with the monitoring module, unit and system as described above, but may also be used for generating a stand-alone spectrometer device as is shown by way of example in fig 2, and as is de- scribed above.
  • this document describes ;a signal monitoring system that uses a polarimeter in the spectrometry of the optical signal, so that the polarization state and the degree of polarization (DOP) can be measured as a function of optical wavelength.
  • DOP degree of polarization
  • the proposed spectrometer module consists of an ele-ment of variable birefringence or differential group delay, DGD, which can have other applications' than measurements of an optical spectrum. Examples of such applica- tions are compensation for and/or emulation] of polarization-mode dispersion, in which a controlled 1 , variable bi- refringence is of great interest.
  • variable birefringence has only been possible by using discrete optics, such as two polarizing beam splitte'rs and mechanical delay line. Such implementations suffer from being bulky, expensive and less mechanically robust.
  • the variable DGD here proposed may have applications also outside the main line of the invention.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

La présente invention concerne un module de spectrométrie comprenant une entrée qui permet de recevoir un signal optique entrant; un élément à temps de propagation de groupe différentiel variable (DGD), qui permet d'appliquer un retard de biréfringence variable audit signal optique entrant; et une unité de détection qui permet de détecter la puissance d'un signal provenant dudit élément DGD, lequel module présente un état de polarisation défini. La présente invention concerne également un module de contrôle, une unité de contrôle et un système de contrôle, comprenant ledit module de spectrométrie utilisé pour contrôler un réseau optique. En outre, cette invention concerne un spectromètre utilisé à des fins de spectrométrie et comprenant un module de spectrométrie tel que défini ci-dessus.
PCT/EP2002/011840 2001-10-23 2002-10-23 Spectrometre WO2003036826A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP01125128A EP1306987A1 (fr) 2001-10-23 2001-10-23 Spectromètre
EP01125128.7 2001-10-23
US09/993,661 US6765670B2 (en) 2001-10-23 2001-11-27 Spectrometer module and applications thereof
US09/993,661 2001-11-27

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WO2003036826A1 true WO2003036826A1 (fr) 2003-05-01

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Citations (4)

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WO1997010658A1 (fr) * 1995-09-15 1997-03-20 Integrated Optical Components Limited Procede permettant de commander separement les puissances des composantes de longueur d'onde dans un systeme de transmission optique a multiplexage par repartition en longueur d'onde
EP0909045A2 (fr) * 1997-09-16 1999-04-14 Lucent Technologies Inc. Procédé et dispositif de compensation automatique de la dispersion de mode de polarisation de premier ordre
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