DE102009043135A1 - Optical filter unit for optical transmission systems, has compensation filter, detector and evaluation unit, where compensation output and two balanced monitor outputs are provided for monitoring signal quality and filter settings - Google Patents

Abstract

The optical filter unit (8) has a compensation filter (9), a detector and an evaluation unit (7). A compensation output (15) and two balanced monitor outputs (16,17) are provided for monitoring the signal quality and filter settings. A transmission line signal (18) spans on the input side of three different delay paths of the compensation filter. The information for monitoring coordination of the compensation filter is realized independently by control unit (24).

Description

The invention relates to an optical filter unit with integrated monitoring of the signal quality in optical transmission systems with wavelength division multiplex or high-speed lines for Internet connections, comprising a compensation filter and at least one detector and an evaluation unit.

An in 1 illustrated conventional optical transmission system 1 consists of a transmitter 2 , a transmission link 3 with a filter 4 and a detector 5 which a data recovery unit 32 containing at least a digital signal processor 6 and an evaluation unit 7 contains, is downstream. The transmission link 3 works in wavelength division multiplexing, causing interference that degrades the transmitted signal.

Therefore, a monitoring - monitoring - of quality parameters of the transmitted signal is necessary.

As a filter unit 8th becomes the component-related combination of filters 4 , Detector 5 , digital signal processor 6 and evaluation unit 7 between which signal interplay exists.

• – die elektronische Entzerrung mittels des digitalen Signalprozessors 6 durchgeführt wird und die Filtereinheit 8 nicht mehrkanalfähig ist, da sie hinter dem Kanalfilter betrieben werden muss,
• – die elektronische Entzerrung einen hohen Energieverbrauch hat, der mit der Kanaldatenrate durch hohe Taktraten steigt und durch die Verarbeitungsleistung und die Geschwindigkeit der elektronischen Bauteile begrenzt ist, wobei
• – der Einsatzort auf der Auswerteeinheit (Rx) 7 beschränkt ist,

wie in der Druckschrift McGhan: Electronic Dispersion Compensation, OFC 2006, Paper OWK1, Tutorial beschrieben ist.For the filter unit 8th according to 1 with the monitoring of the quality parameters, the method of electronic equalization is used, wherein in the filter unit 8th

• - the electronic equalization by means of the digital signal processor 6 is performed and the filter unit 8th is not multi-channel capable, since it must be operated behind the channel filter,
• - The electronic equalization has a high energy consumption, which increases with the channel data rate by high clock rates and is limited by the processing power and the speed of the electronic components, wherein
• - the location on the evaluation unit (Rx) 7 is limited

as described in McGhan: Electronic Dispersion Compensation, OFC 2006, Paper OWK1, Tutorial.

The signal quality / signal quality is defined such that the symbols at the receiver can be distinguished from each other without error.

The quality parameters of a transmittable optical signal are optical signal-to-noise ratio (OSNR), eye aperture, Q-factor. You will u. a. influenced by dispersion and noise.

On the other hand, conventionally, instead of a channel filter 4 with electronic equalization use of an optical compensation filter 9 for equalization, extraction of signal components, or use of the receiver bit error rate to iteratively match the filter 4 set filter coefficients κ set.

The signals are received by means of photodiodes 5 and the evaluation unit 7 ,

In 2a is the compensation filter 9 the detector 5 as well as the evaluation unit 7 , from which a feedback signal line 10 to the compensation filter 9 emanating, arranged in order.

In 2 B are branching connections in front of and behind the compensation filter 9 for the optical and electronic processing in an evaluation unit 7 available for analysis. There is no data recovery.

• – zur Überwachung – zum Monitoring – ein komplizierter Aufbau des optischen Kompensationsfilters 9 erforderlich ist,
• – eine schwierige Einstellung des optischen Kompensationsfilters 9 vorhanden ist, da nur die Bitfehlerrate als Kriterium vorhanden ist und die Einstellung probiert werden muss,
• – die elektronische Entzerrung dabei nicht mehrkanalfähig ist,
• – die elektronische Entzerrung einen hohen Energieverbrauch hat, der mit der Kanaldatenrate steigt, bedingt durch hohe Taktraten, und durch die Verarbeitungsleistung und die Geschwindigkeit der elektronischen Bauteile begrenzt ist,
• – der Einsatzort dabei auf die Auswerteeinheit 7 beschränkt ist.

The disadvantages of the solutions with a compensation filter 9 consist in that

• - for monitoring - for monitoring - a complicated structure of the optical compensation filter 9 is required,
• - a difficult setting of the optical compensation filter 9 is present, since only the bit error rate is present as a criterion and the setting must be tried
• - the electronic equalization is not multi-channel capable,
• The electronic equalization has a high energy consumption, which increases with the channel data rate, is limited by high clock rates, and is limited by the processing power and the speed of the electronic components,
• - The place of use on the evaluation unit 7 is limited.

In the schematic circuits of 2a . 2 B each have a linear detection available.

In the 2a . 2 B and in 3 For example, optical filters exist as compensation filters in transmission systems that are referred to as fiber Bragg gratings in the document US 2004/0037505 A1 , as Arrayed Waveguide Gratings in the publication US Pat. No. 7,403,682 B1 and as optical delay line filters (serial, parallel) in the document US Pat. No. 7,106,923 B1 as well as in the publications US 7,536,108 B2 and US 6,370,300 B1 are specified and described.

The problems of these solutions are that a difficult setting of the optical compensation filters 9 is present, since only the bit error rate is present as a criterion and the Setting must be made iteratively or with heuristics, the setting is slow and there is no guaranteed convergence.

Furthermore, the compensation filters 9 a complicated structure, wherein a part of the transmitted signal before and / or after the compensation filter 9 which is an additional implementation of an analysis filter as well as optical and electronic components for an electronic evaluation unit 7 require.

For recording the signals and for their further processing, according to the prior art, a linear detection and a non-linear detection can be used, as in the following documents Inui et al .: 160 Gbps Adaptive Dispersion Equalization Using Asynchronous Dispersion-induced Chirp Monitor, Journal of Lightwave Technology, Vol. 6, p. 2038 ff. and Wielandy et al .: Demonstration of automatic dispersion control for 160 Gbps transmission over 275 km of deployed fiber, Electronics Letters of 27.05.2004, Vol. 11 , is described.

In the 3 The non-linear detection described in the above-cited references provides a transmitted output signal proportional to the pulse width for the same power, with the existing dispersion D _signal widening the pulses. Thus, a dispersion estimate is made via the non-linear detection, whereby the positive dispersion + D and the negative dispersion -D widen to the same extent.

The sign - plus / minus - of the dispersion D can not be determined directly. This results in a differential structure:

Splitting the incident signal D _signal into a path 11 with positive additional dispersion + D and a path with negative additional dispersion -D, whereby, depending on the sign of the dispersion D, the pulse width in the path 11 with positive additional dispersion + D or in the path 12 with negative additional dispersion -D decreases and from the difference of the signals in the path 11 with positive dispersion P _n1 and in the path 12 with negative dispersion P _n2 gives the sign, as in the document Inui et al .: 160 Gbps Adaptive Dispersion Equalization Using Asynchronous Dispersion-induced Chirp Monitor, Journal of Lightwave Technology, Vol. 6, p. 2038 ff. is described.

The invention has for its object to provide an optical filter unit with integrated monitoring of the signal quality in optical transmission systems, which is constructed so suitable that the signal interference can be compensated and at the same time the compensation function, in particular the vote on channel spacing is monitored. It is intended to simplify the structure of the filter unit and, in particular, the compensation filter in order to be able to autonomously realize with the module a compensation of the compensation filter on a WDM channel and a compensation of disturbances. In addition, a matching control algorithm should be specified.

The invention is solved by the features of claim 1. The optical filter unit with integrated monitoring of the signal quality in optical transmission systems with wavelength division multiplex or high-speed lines for Internet connections, comprising a compensation filter and at least one detector and an evaluation unit, has according to the characterizing feature of patent claim 1

• - at least two symmetrical monitor outputs for monitoring the signal quality and filter setting are present in the compensation filter on the output side next to the compensation output corresponding to the middle of the channel,
• Wherein the transmission path signal initially passes over at least three differently delayed paths of the compensation filter, which has a 3 × 3 coupler at least in the output region,
• - Wherein detection is provided at the monitor outputs of the 3 × 3 coupler and
• - By means of the information from the monitoring, the tuning of the compensation filter by means of a detection of the subsequent control unit in the evaluation unit is autonomously realized.

The compensation filter may be designed as a Mach-Zehnder interferometer, in particular as a delay line filter.

The detection may be formed as a linear detection and / or as a non-linear detection.

• – neben dem Kompensationsausgang entsprechend zur Kanalmitte f_m ausgebildete symmetrische Monitor-Ausgänge mit einer Übertragungsfunktion H_mon1 am ersten Monitor-Ausgang und einer Übertragungsfunktion H_mon2 am zweiten Monitor-Ausgang nach der Gleichung H_mon1(f_m + f) = H_mon2(f_m – f) (1) zur Überwachung der Signalqualität und der Filtereinstellung besitzt, wobei f_m die Frequenz in der Kanalmitte und f eine beliebige Frequenz des Signals ist,
• – wobei an den Monitor-Ausgängen eine nichtlineare Detektion und/oder eine lineare Detektion vorgesehen sind,
• – wodurch die Lage des Kompensationsfilters in Bezug auf das Kanalraster einschätzbar ist, wobei die Regelung auf dem ersten Monitorausgang minus dem zweiten Monitorausgang = 0 ist und die Richtung durch den Anstieg determiniert ist und
• – wodurch die Störgrößen des übertragenen Signals messbar sind.

The optical compensation filter with integrated monitoring of the signal quality in optical transmission systems in the context of the optical filter unit has

• - In addition to the compensation output corresponding to the channel center f _m trained symmetrical monitor outputs with a transfer function H _mon1 at the first monitor output and a transfer function H _mon2 at the second monitor output according to the equation H _mon1 (f _m + f) = H _mon2 (f _{m -f} ) (1) for monitoring the signal quality and the filter setting, where f _{m is} the frequency in the Channel center and f is any frequency of the signal,
• Wherein a non-linear detection and / or a linear detection are provided at the monitor outputs,
• - whereby the position of the compensation filter with respect to the channel grid can be estimated, the control on the first monitor output minus the second monitor output = 0 and the direction is determined by the rise and
• - By which the disturbances of the transmitted signal can be measured.

The advantages of the invention are that there is a filter unit whose filter can both compensate for disturbances and provide information that is used to tune the compensation filter. The functionality of the compensation of signal interference and the monitoring functionality influence each other. At least two monitoring outputs with transfer functions symmetrical to the middle of the channel provide enough information to deterministically tune the compensation filter. The compensation functionality is retained.

• – eine einfache und autonome Abstimmbarkeit des optischen Kompensationsfilters mit
• – einer Abstimmung auf das Kanalraster
• – einer Abstimmung auf die Kompensationsfunktion in Bezug auf die Streckenstörungen sowie
• – eine deterministische Einstellung erreicht.

It gets it

• A simple and autonomous tunability of the optical compensation filter with
• - a vote on the channel grid
• - a vote on the compensation function in terms of the route noise as well
• - reached a deterministic setting.

Further developments and advantageous embodiments of the invention are specified in further subclaims.

The invention will be explained in more detail by means of an embodiment with reference to drawings:

Show it:

1 a schematic representation of the electronic compensation according to the prior art,

2 schematic representations of optical compensations according to the prior art, wherein

2a a compensation representation with iterative attitude and

2 B show a compensation representation with branched useful signal,

3 a schematic representation with non-linear detection according to the prior art,

4 a schematic representation of the filter unit according to the invention,

5 a schematic representation of an optical compensation filter according to the invention with symmetrical monitor outputs,

6 a flow diagram for the sequence of a filter control with linear detection,

7 Load frequency curves

8th a flowchart for the sequence of a filter control with non-linear detection,

9 a schematic representation of a filter unit with a circuit combination of linear detection and non-linear detection and

10 a flowchart for the flow of a filter control with linear detection and non-linear detection according to 9 ,

The following are the 4 . 5 considered together.

In 4 is a general schematic structural position of the optical filter unit according to the invention 8th shown, which consists of a compensation filter 9 with a compensation output 15 and with at least two monitor outputs 16 . 17 , where the monitor outputs 16 . 17 symmetrical with each other and with an evaluation unit 7 in the modules for evaluation with linear detection 23a and / or nonlinear detection 23b and one on the symmetry of the monitor outputs 16 . 17 coordinated, autonomous control of the compensation filter 9 by means of a control unit 24 available.

In 5 is a schematic representation of the optical compensation filter 9 with symmetrical monitor outputs 16 . 17 shown, wherein in a special case, a second-order optical filter with two monitor outputs is specified. The optical filter is a compensation filter 9 which consists of a first coupler 22 with the coupling coefficient κ ₂ and a second coupler 25 with the coupling coefficient κ ₁ , wherein the second coupler 25 on the input side as input three signal feeds 18 and the first coupler 22 on the output side, three outputs 15 . 16 . 17 has, wherein the average output 15 the compensation output and the outputs next to it 16 . 17 represent symmetrical monitor outputs, with between the two couplers 25 . 22 each different delay lines 19 . 20 . 21 that the signal feeds 18 and the outputs 15 . 16 . 17 connect each other, and each with a phase shifter 26 . 27 . 28 are provided.

• – die Wahl der Koppelkoeffizienten κ₁, κ₂ und der Phasenschieber 26 Φ₁, 27 Φ₂, 28 Φ₃ derart erfolgt, dass eine Symmetrie von erstem Monitor-Ausgang 16 und zweitem Monitor-Ausgang 17 entsteht sowie eine Kompensationsfunktion realisiert wird, wobei die beiden Koppler 22, 25 als identische Koppler κ₁ = κ₂ = κ eine gleiche Phaseneinstellung Φ₁ = Φ₃ haben und
• – die Einstellung der Kompensationsart und des Kompensationsbereiches über die Koppelkoeffizienten κ und die Phasenschieber 16, 27, 28 mit Φ₁ = – Φ₃ und Φ₂ abläuft.

The operation is designed such that

• - The choice of coupling coefficients κ ₁ , κ ₂ and the phase shifter 26 Φ ₁ , 27 Φ ₂ , 28 Φ _{3 is} such that a symmetry of the first monitor output 16 and second monitor output 17 arises as well as a compensation function is realized, wherein the two couplers 22 . 25 as identical couplers κ ₁ = κ ₂ = κ have a same phase setting Φ ₁ = Φ ₃ and
• - The setting of the compensation type and the compensation range on the coupling coefficients κ and the phase shifter 16 . 27 . 28 with Φ ₁ = - Φ ₃ and Φ ₂ expires.

The matching, symmetry of the monitor outputs 16 . 17 to the channel-centered compensation output 15 exploiting evaluation methods for the control is carried out as follows:

• – für das Signal in der Kanalmitte mit erstem Monitor-Ausgang 16 – zweitem Monitor-Ausgang 17 = 0 gilt und
• – für das Signal abseits der Kanalmitte mit erstem Monitor-Ausgang 16 – zweitem Monitor-Ausgang 17 eine Regelgröße proportional zum Frequenzabstand zur Kanalmitte geliefert wird.

In 6 is a flowchart for the flow of a filter control with linear detection 23a shown, where there is an evaluation by means of linear detection, z. B. is indicated with a channel centering and an adjustment to the transmitted power, wherein the centering by symmetrical monitor functions at the first monitor output 16 and the second monitor output 17 takes place, where

• - for the signal in the middle of the channel with the first monitor output 16 - second monitor output 17 = 0 applies and
• - for the signal off the middle of the channel with the first monitor output 16 - second monitor output 17 a control variable is supplied proportional to the frequency distance to the center of the channel.

• – Messung der Leistungen P₁, P₂ an den Monitor-Ausgängen 16, 17,
• – Auswertung der gemessenen Leistungen P₁, P₂ in der Auswerteeinheit 7, ob die gemessenen Leistungen P₁, P₂ kleiner als eine Minimalleistung P_min mit P₁ < P_min und P₂ < P_min sind,
• – Feststellung in der Auswerteeinheit 7, ob bei Erfüllung dieser Bedingungen das Kompensationsfilter 9 angepasst ausgebildet ist oder ob bei Nicht-erfüllung dieser Bedingungen der Leistungsunterschied |P₁ – P₂| größer als ein Leistungs-Grenzwert P_thres mit |P₁ – P₂| > P_thres ist, so dass eine Zentrierung des Kompensationsfilters 9 mittels der Steuereinheit 24 gemäß der Gleichung Δλ = Δλ(P₁ – P₂) bei den zugehörigen Phaseneinstellungen nach Gleichung Φ₁ = Φ₃ = Φ₃ (Δλ) durchgeführt wird, oder
• – Feststellung in der Auswerteeinheit 7, ob der Leistungsunterschied |P₁ – P₂| kleiner als ein Leistungs-Grenzwert P_thres mit |P₁ – P₂| < P_thres ist, so dass die Übertragungsfunktion (Φ₂ → P₁, P₂ min) für eine maximale Transmission und der Leistungs-Grenzwert P_thres angepasst werden, so dass eine Zentrierung des Kompensationsfilters 9 mittels der Steuereinheit 24 nach der Gleichung Δλ = Δλ(P₁ – P₂) bei den zugehörigen Phaseneinstellungen nach Gleichung = Φ₃ = Φ₃(Δλ) durchgeführt wird.

The filter control takes place according to 6 according to the following procedure:

• - Measurement of the power P ₁ , P ₂ at the monitor outputs 16 . 17 .
• - Evaluation of the measured power P ₁ , P ₂ in the evaluation unit 7 whether the measured powers P ₁ , P _{2 are} smaller than a minimum power P _min with P ₁ <P _min and P ₂ <P _min ,
• - Detection in the evaluation unit 7 , if at fulfillment of these conditions the compensation filter 9 has been adapted or whether the performance difference | P ₁ - P ₂ | greater than a power limit P _thress with | P ₁ - P ₂ | > P _thres is, allowing a centering of the compensation _filter 9 by means of the control unit 24 is performed according to the equation Δλ = Δλ (P ₁ -P ₂ ) at the associated phase settings according to equation Φ ₁ = Φ ₃ = Φ ₃ (Δλ), or
• - Detection in the evaluation unit 7 whether the power difference | P ₁ - P ₂ | less than a power limit P _thress with | P ₁ - P ₂ | <P _thres is _adjusted so that the transfer function (Φ ₂ → P ₁ , P ₂ min) for maximum transmission and the power limit P _thres , so that centering of the compensation _filter 9 by means of the control unit 24 is carried out according to the equation Δλ = Δλ (P ₁ -P ₂ ) at the associated phase settings according to equation = Φ ₃ = Φ ₃ (Δλ).

The associated power frequency curves are in 7 illustrated, wherein the input power P _in on the losses L of the structure, the output power P _{mon1 of} the first monitor output 16 , the output power P _{mon2 of} the second monitor output 17 and the output power P _{out of} the compensation output 15 is divided according to equation P _{into -L} = P _mon1 + P _mon2 + P _out and wherein the output _powers P _mon1 + P _mon2 must be minimized in total upon reaching a maximum compensation output power P _out .

• – durch symmetrische Monitorfunktionen (und damit auch Dispersionsfunktionen) sind die Monitorfunktionen als Aufteilung in D₁ = +D-Pfad und D₂ = –D-Pfad nutzbar, wobei das Verfahren nicht nur bei dem vorteilhaften +D/–D funktioniert, sondern auch bei unterschiedlichem D₁, D_2.,
• – Dispersionsmonitoring durch pulsbreitenabhängiges nichtlineares Signal für die Ausgangsleistungen P_N1, P_N2.

In 8th is for an equal compensation filter 9 a flowchart for the flow of a filter control with non-linear detection 23b indicated, wherein the evaluation by means of non-linear detection 23b , z. B. by means of a dispersion estimate

• - By symmetric monitor functions (and thus also dispersion functions), the monitor functions as a division into D ₁ = + D-path and D ₂ = -D-path can be used, the method not only works in the advantageous + D / -D, but also with different D ₁ , D ₂ ,
• Dispersion monitoring by pulse-width-dependent non-linear signal for the output powers P _N1 , P _N2 .

• – Messung der nichtlinearen Leistungen P_N1, P_N2 an den Monitor-Ausgängen 16, 17,
• – Bestimmung der Dispersion D nach der funktionalen Abhängigkeit D = D(P_N1, P_N2),
• – Einstellung des Kompensationsfilters 9 auf den Zustand zur Dispersionskompensation nach der funktionalen Abhängigkeit Φ₂ = Φ₂(D).

The filter control takes place according to 8th according to the following procedure:

• - Measurement of the non-linear powers P _N1 , P _N2 at the monitor outputs 16 . 17 .
• Determination of the dispersion D according to the functional dependence D = D (P _N1 , P _N2 ),
• - Setting the compensation filter 9 to the state for dispersion compensation according to the functional dependence Φ ₂ = Φ ₂ (D).

In 9 is a schematic representation of a filter unit 8th with a compensation filter according to the invention 9 and with a circuit combination 29 from linear detection 5 and nonlinear detection 23b indicated, with the compensation filter 9 is first centered and then adjusted according to dispersion estimation, wherein the amplitude transfer function of the compensation filter 9 serves as a control for filter adjustment.

• – einem Kompensationsfilter 9 mit einem Kompensationsausgang 15 und zwei Monitor-Ausgängen 16, 17 mit D₁ und D₂,
• – einem linearen Detektor 5 zur linearen Detektion 23a,
• – einem nichtlinearen Detektor 13 zur nichtlinearen Detektion 23b,
• – einem Umschalter 30 zwischen den Monitor-Ausgängen 16, 17 und den beiden Detektoren 5, 13, wobei durch den Umschalter 30 nur der lineare Detektor 5 und der nichtlineare Detektor 13 wechselseitig für den ersten Monitor-Ausgang 16 und für den zweiten Monitor-Ausgang 17 zuschaltbar ist,
• – einer Steuereinheit 24, die mit den beiden Detektoren 5, 13 einerseits und mit dem Kompensationsfilter 9 andererseits über mindestens eine Verbindungsleitung 31 in Verbindung steht.

The structure of a filter unit 8th is in principle equipped with the following elements: with

• - a compensation filter 9 with a compensation output 15 and two monitor outputs 16 . 17 with D ₁ and D ₂ ,
• - a linear detector 5 for linear detection 23a .
• - a nonlinear detector 13 for nonlinear detection 23b .
• - a switch 30 between the monitor outputs 16 . 17 and the two detectors 5 . 13 , where by the switch 30 only the linear detector 5 and the nonlinear detector 13 alternately for the first monitor output 16 and for the second monitor output 17 is switchable,
• - a control unit 24 that with the two detectors 5 . 13 on the one hand and with the compensation filter 9 on the other hand via at least one connecting line 31 communicates.

• – Messung der Leistungen P₁, P₂ an den Monitor-Ausgängen 16, 17,
• – Feststellung in der Auswerteeinheit 7, ob der Leistungsunterschied |P₁ – P₂| größer als ein Leistungs-Grenzwert P_thres mit |P₁ – P₂| > P_thres ist, so dass eine Zentrierung des Kompensationsfilters 9 mittels der Gleichung Δλ = Δλ(P₁ – P₂) bei den zugehörigen Phaseneinstellungen nach Gleichung Φ₁ = Φ₃ = Φ₁(Δλ) mit Hilfe der Steuereinheit 24 durchgeführt wird, oder
• – Feststellung in der Auswerteeinheit 7, ob der Leistungsunterschied |P₁ – P₂| kleiner als der Leistungs-Grenzwert P_thres mit |P₁ – P₂| < P_thres ist, so dass eine Umschaltung der Monitor-Ausgänge 16, 17 mittels des Umschalters 30 erfolgt,
• – Messung der nichtlinearen Leistungen P_N1, P_N2 an den Monitor-Ausgängen 16, 17,
• – Bestimmung der Dispersion D mit D = D(P_N1, P_N2),
• – Einstellung des Kompensationsfilters 9 auf den Zustand zur Dispersionskompensation nach Gleichung Φ₂ = Φ₂(D),
• – Anpassung des Leistungs-Grenzwertes P_thres auf den Filterzustand,
• – Zentrierung des Kompensationsfilters 9 mittels der Gleichung Δλ = Δλ(P₁ – P₂) bei den zugehörigen Phaseneinstellungen nach Gleichung Φ₁ = Φ₃ = Φ₃(Δλ) mittels der Steuereinheit 24.

In 10 FIG. 10 is a flowchart for the flow of a filter control with a linear detection 23a and a nonlinear detection 23b to 9 with the aim of centering and adjusting the compensation filter 9 are provided on a dispersion compensation:

• - Measurement of the power P ₁ , P ₂ at the monitor outputs 16 . 17 .
• - Detection in the evaluation unit 7 whether the power difference | P ₁ - P ₂ | greater than a power limit P _thress with | P ₁ - P ₂ | > P _thres is, allowing a centering of the compensation _filter 9 by the equation Δλ = Δλ (P ₁ -P ₂ ) at the associated phase settings according to equation Φ ₁ = Φ ₃ = Φ ₁ (Δλ) by means of the control unit 24 is performed, or
• - Detection in the evaluation unit 7 whether the power difference | P ₁ - P ₂ | less than the power limit P _thress with | P ₁ - P ₂ | <P _thres is, allowing a switching of the monitor outputs 16 . 17 by means of the switch 30 he follows,
• - Measurement of the non-linear powers P _N1 , P _N2 at the monitor outputs 16 . 17 .
• Determination of the dispersion D with D = D (P _N1 , P _N2 ),
• - Setting the compensation filter 9 to the state for dispersion compensation according to equation Φ ₂ = Φ ₂ (D),
• Adaptation of the power limit value P _threshes to the filter condition,
• - Centering of the compensation filter 9 by the equation Δλ = Δλ (P ₁ -P ₂ ) at the associated phase settings according to equation Φ ₁ = Φ ₃ = Φ ₃ (Δλ) by means of the control unit 24 ,

LIST OF REFERENCE NUMBERS

1

transmission system

2

transmitter

3

transmission path

4

filter

5

detector

6

signal processor

7

evaluation

8th

filter unit

9

compensating filter

10

feedback

11

first path

12

second path

13

nonlinear detector

14

switch

15

compensation output

16

first monitor output

17

second monitor output

18

input signal feeds

19

first delay line

20

second delay line

21

third delay line

22

coupler

23

detection

23a

linear detection

23b

nonlinear detection

24

control unit

25

second coupler

26

first phase shifter

27

second phase shifter

28

third phase shifter

29

Circuit combination

30

switch

31

connecting line

32

Data recovery unit

DSP

digital signal processor

Rx

receiver

D

dispersion

D ₁

first dispersion 1

D ₂

second dispersion 2

D _signal

Dispersion of the signal 18

+ D path

with positive additional dispersion

-D path

with negative additional dispersion

κ

coupling coefficient

κ ₁

first coupling coefficient

^κ 2

second coupling coefficient

Φ

phasing

Φ ₁

first phase adjustment

₂

second phase adjustment

Φ ₃

third phase adjustment

λ

wavelength

Δλ

Wavelength difference

T

Retarder / track

P _mon1

input power

L

losses

P _mon2

Output power at the first monitor output

P _mon2

Output power at the second monitor output

P _out

output

P _thres

Power limit value

P ₁

Performance of linear detection

P ₂

Performance of linear detection

P _N1

Performance of nonlinear detection

P _N2

Performance of nonlinear detection

f

frequency

f _m

Frequency for the channel center

H _mon1

Transfer function of the first monitor output

H _mon2

Transfer function of the second monitor output

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2004/0037505 A1 [0014]
• US 7403682 [0014]
• US 7106923 B1 [0014]
• US 7536108 B2 [0014]
• US 6370300 B1 [0014]

Cited non-patent literature

• Inui et al .: 160 Gbps Adaptive Dispersion Equalization Using Asynchronous Dispersion-induced Chirp Monitor, Journal of Lightwave Technology, Vol. 6, p. 2038 et seq. [0017]
• Wielandy et al .: Demonstration of automatic dispersion control for 160 Gbps transmission over 275 km of deployed fiber, Electronics Letters of 27.05.2004, Vol. 11 [0017]
• Inui et al .: 160 Gbps Adaptive Dispersion Equalization Using Asynchronous Dispersion-induced Chirp Monitor, Journal of Lightwave Technology, Vol. 6, p. 2038 et seq. [0020]

Claims (12)

Optical filter unit ( 8th ) with integrated monitoring of the signal quality in optical transmission systems ( 1 ) with wavelength division multiplex or high-speed Internet connection links, comprising a compensation filter ( 9 ) and at least one detector ( 5 ) and an evaluation unit ( 7 ), characterized in that - in the compensation filter ( 9 ) on the output side next to the compensation output ( 15 ) at least two symmetrical monitor outputs corresponding to the middle of the channel ( 16 . 17 ) are provided for monitoring the signal quality and filter setting, - wherein the transmission path signal ( 18 ) on the input side via at least three differently delayed paths ( 19 . 20 . 21 ) of the compensation filter ( 9 ) running, at least in the exit region, a 3 × 3 coupler ( 22 ), - where at the monitor outputs ( 16 . 17 ) of the 3 × 3 coupler ( 22 ) at least one detection ( 23 ) and - whereby by means of the information from the monitoring the tuning of the compensation filter ( 9 ) by means of one of the detection ( 23 ) subsequent control unit ( 24 ) in the context of the evaluation unit ( 7 ) is autonomously realizable. Filter unit according to claim 1, characterized in that the compensation filter ( 9 ) is designed as a Mach-Zehnder interferometer. Filter unit according to claim 1, characterized in that the Mach-Zehnder interferometer ( 9 ) is designed as a delay line filter. Filter unit according to claim 1, characterized in that the detection ( 23 ) as linear detection ( 23a ) and / or as non-linear detection ( 23b ) is trained. Filter unit according to at least one of the preceding claims, characterized in that the optical compensation filter ( 9 ) - next to the compensation output ( 15 ) according to the channel center (f _m ) symmetrical monitor outputs ( 16 . 17 ) with a transfer function H _mon1 at the first monitor output ( 16 ) and a transfer function H _mon2 at the second monitor output ( 17 ) according to the equation H _mon1 (f _m + f) = H _mon2 (f _{m -f} ) (I) for monitoring the signal quality and the filter setting, where f _{m is} the frequency in the middle of the channel and f is any frequency of the signal, - where at the monitor outputs ( 16 . 17 ) a linear detection ( 23a ) and / or a non-linear detection ( 23b ), whereby the position of the compensation filter ( 9 ) is estimable with respect to the channel grid, with the control on the first monitor output 16 minus the second monitor output 17 = 0 and the direction is determined by the rise and - whereby the disturbances of the transmitted signal ( 18 ) are measurable. Filter unit according to at least one of the preceding claims, characterized in that the compensation filter ( 9 ) compensates for disturbances as well as supplies information necessary for tuning the compensation filter ( 9 ) are usable. Filter unit according to at least one of the preceding claims, characterized in that it consists of a compensation filter ( 9 ) with a compensation output ( 15 ) and with at least two monitor outputs ( 16 . 17 ), with the monitor outputs ( 16 . 17 ) are symmetrical to each other and with an evaluation unit ( 6 ) in the modules for evaluation with linear detection ( 23a ) and / or nonlinear detection ( 23b ) and one on the symmetry of the monitor outputs ( 16 . 17 ), autonomous control of the compensation filter ( 9 ) by means of the control unit ( 24 ) available. Filter unit according to at least one of the preceding claims, characterized in that the optical compensation filter ( 9 ) with symmetrical monitor outputs ( 16 . 17 ) is a 2nd order optical filter with two monitor outputs. Filter unit according to at least one of the preceding claims, characterized in that the compensation filter ( 9 ) from a first coupler ( 22 ) with the coupling coefficient (κ ₂ ) and a second coupler ( 25 ) with the coupling coefficient (κ ₁ ), wherein the second coupler ( 25 ) on the input side as input three signal feeds ( 18 ) and the first coupler ( 22 ) on the output side three outputs ( 15 . 16 . 17 ), the middle output ( 15 ) the compensation output and the adjacent outputs ( 16 . 17 ) symmetrical monitor outputs, whereby between the two couplers ( 25 . 22 ) each have different delay lines ( 19 . 20 . 21 ), the signal feeds ( 18 ) and the outputs ( 15 . 16 . 17 ) are connected to each other, are present and wherein the delay lines ( 19 . 20 . 21 ) each with a phase shifter ( 26 . 27 . 28 ) are provided. Filter unit according to at least one of the preceding claims, characterized that they have a tuned, symmetry of monitor outputs ( 16 . 17 ) to the channel-centered compensation output ( 15 ) exploiting evaluation method for controlling the compensation filter ( 9 ) having. Filter unit according to at least one of the preceding claims, characterized in that it is provided with a compensation filter ( 9 ) and with a subordinate circuit combination ( 29 ) from linear detection ( 5 ) and / or nonlinear detection ( 23b ), the compensation filter ( 9 ) is first centered and then adjusted according to dispersion estimation, wherein the amplitude transfer function of the compensation filter ( 9 ) as a control parameter for filter adjustment by the control unit ( 24 ) serves. Filter unit according to at least one of the preceding claims, characterized in that it is equipped with the following elements, with - a compensation filter ( 9 ) with a compensation output ( 15 ) and two monitor outputs ( 16 . 17 ) with a respective dispersion D ₁ and D ₂ , - a linear detector ( 5 ), - a nonlinear detector ( 13 ), - a switch ( 30 ) between the monitor outputs ( 16 . 17 ) and the two detectors ( 5 . 13 ), whereby by the switch ( 30 ) only the linear detector ( 5 ) and the nonlinear detector ( 13 ) alternately for the first monitor output ( 16 ) and for the second monitor output ( 17 ), - a control unit ( 24 ), with the two detectors ( 5 . 13 ) on the one hand and with the compensation filter ( 9 ) via at least one connecting line ( 31 ) on the other hand.

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