CN101371470A - Optical signal measurement system - Google Patents

Abstract

An optical signal measurement system [1200] provides [1202] a tunable optical filter [402]. An unknown optical signal [628] is scanned [1204] through the tunable optical filter [402]. The wavelength and chromatic dispersion values of the unknown optical signal [628] scanned through the tunable optical filter [402] are measured [1206] by operating the tunable optical filter [402] in a scanning mode for at least one of OSA and PMD measurements, and in a stepping mode for CD measurements. The wavelength and the dispersion values in the unknown optical signal [628] are specified [1208].

Description

Optical signal measurement system

The mutual reference of related application

The application's case is advocated in the U.S. Provisional Patent Application case (provisional patent application) the 60/757th of proposition on January 10th, 2006, the priority of the 11/615th, No. 986 case of U.S. patent application case of the non-interim case (nonprovisional) of No. 961 cases.

The application's case contains and is present in the 11/048th, No. 455 relevant target of case of U.S. patent application case that on January 31st, 2005 proposed jointly, and this relevant application case is amortized and given Sunrise Telecom Inc. (Sunrise Telecom Incorporated).

The application's case also contains and is present in the 11/329th, No. 522 relevant target of case of U.S. patent application case that on January 10th, 2006 proposed jointly, and this relevant application case is amortized and given Sunrise Telecom Inc..

Technical field

Relevant substantially spectrum of the present invention and chromatic dispersion analysis, and relevant especially wide wave-length coverage spectrum polarization mode and the chromatic dispersion analyzer (broad wave length range optical spectrum polarization mode andchromatic dispersion analyzer) that uses Fabry-Perot optical filter (Fabry-Perot filter).

Background technology

Fiber optic telecommunications (Telecommunication is called for short telecom) field comprises the technology such as Connectorized fiber optic cabling and fiber optic network.Fiber optic network carries such as dialogue, data communication (for example, fax message), computer to multiple daily information signals such as the transfer of data of computer, cable TV, the Internets.This kind information signal is transmitting between the city and between the area, incity, city.Because the communication flows (traffic) that increases sharply, so during with the comparing than low capacity of old-fashioned metal cable, the amplification capacity of Connectorized fiber optic cabling is more and more necessary.

Usually constitute Connectorized fiber optic cabling by a branch of other optical fiber.Article one, single optical fiber can carry thousands of data and signal of communication on single optical wavelength.This identical single optical fiber also can carry a plurality of optical wavelength, thereby makes this single optical fiber can carry many multiple light signals simultaneously.Each wavelength can surpass carry data under the transmission rate of 10,000,000,000 bit/second (Gbit/s) separately.

In order to dispose this kind fiber optic network and to keep its communication, must carry out various sensitivity analyses, for example, measure chromatic dispersion and Polarization Dispersion (polarization dispersion), monitor luminous power, wavelength, reach the light signal noise and compare etc. by the light signal each wavelength of optical fiber under.Traditionally, by wherein comprising chromatic dispersion (Chromatic Dispersion; Abbreviation CD) analyzer, polarisation mode dispersion (Polarization Mode Dispersion; Be called for short PMD) analyzer and spectroanalysis instrument (Optical Spectrum Analyzer; Abbreviation OSA) several analysis tools are carried out this alanysis.

Chromatic dispersion means the light with different wave length and passes through medium with different speed.When optical fiber is passed through in the light pulse that contains the different wave length composition, will broaden because of CD.There are several to measure the mode of CD.A kind of method is the measurement that postpones according to the relative time that has between wavelength optical signals, and carries out the chromatic dispersion analysis.

Polarisation mode dispersion means the light with different polarization modes and passes through medium with different speed.When optical fiber is passed through in the light pulse that contains different polarization modes, will broaden because of PMD.There are several to measure the mode of PMD.A kind of method is called as " stationary analyzer (Fixed Analyzer) " method.When using this kind method, measure also the relatively full optical power distribution of light signal and the optical power distribution of particular polarization pattern, and from the counting of the peak value of the ratio of luminous power frequency spectrum, and derive PMD.

OSA carries out spectrum analysis (being also referred to as " OSA "), shows that as its name referring spectrum analysis is the measurement to the luminous power that becomes along with wavelength.The application of OSA comprises: testing laser and (or) light-emitting diode (Light-Emitting Diode; Abbreviation LED) spectral purity and the distribute power of light source; Monitor wavelength division multiplexed (Wavelength Division Multiplexing; Abbreviation WDM) signal quality and the noise figure (noise figure) of the light conveying system of system; Test the transmission characteristic of various electro-optical devices and assembly etc.

Usually via tunable optical filter (optical filter) transmit will be analyzed light signal, and carry out OSA." tunable " means: tunable optical filter, so that resolve or sort out indivedual compositions (wavelength) of light signal.

The optical filter of three kinds of fundamental types is widely used for making OSA: diffraction grating (diffraction grating), Fabry-Perot (FP) optical filter and Michelson's interferometer (Michelson interferometer).Tunable FP optical filter (Tunable FPFilter; Abbreviation TFPF) has the many advantages that are used for OSA.Major advantage in these advantages is its relatively simply design, small size, fast speed, be easy to control, with and be used for difference at interval hand-to-hand light signal (that is, have much at one frequency or the signal of wavelength) high sensitive.

Lens are tunable FP interferometer (FP Interferometer; Be called for short FPI) for a long time physics, chemistry, astronomy, and other multiple scientific domains in spectral measurement in played the part of important role.The micro lens FPI that is applicable to fibre system can provide middle resolution tuning (accuracy (finesse)=100).Yet, no lens fiber FPI (Fiber FPI; Be called for short FFPI) can under greater than 500 resolution, carry out the tuber function in the fibre system.The dynamical tunable FFPI of this kind can allow long distance recognition system (interrogator system) be used for measuring exactly passive or the initiatively wavelength response of fiber device.

The light resolution of OSA is the minimum wavelength interval between two spectral components can being resolved reliably.In order to realize high light resolution, optical filter should have 3 decibels of enough narrow frequency range (bandwidth; Be called for short BW).In addition, for many measurements, various spectral components that will be measured do not have equal amplitude, and in this kind situation, the BW of optical filter is not unique consideration point.(the light rejection for example, ± 25GHz) is than (Optical Rejection Rate according to leaving a certain distance of transfer peak; Be called for short ORR) and the shape of the optical filter of appointment also is important.Example comprises: measure distribution feedback type (Distributed Feedback; Abbreviation DFB) edge mode of laser suppresses (side-mode suppression); And the light signal noise of the various wavelength channels in the measurement wdm optical communication system is than (Optical Signal-to-NoiseRatio; Be called for short OSNR).

The wavelength scanning range of FP optical filter OSA is subjected to its free spectral range (FreeSpectrum Range; Abbreviation FSR) restriction.For identical precision value, the BW of FP optical filter is directly proportional with its FSR, and this promptly means: FSR is bigger, and then BW is bigger, and resolution is poorer.Therefore, for many FP optical filter OSA use, two main challenges are arranged.A challenge is to realize that the light signal noise (for example, is used for dense wavelength and cuts apart multiplexed (Dense Wavelength DivisionMultiplexing than the high dynamic range that (S/N) measures; Abbreviation DWDM) specificity analysis of system).Another challenge is the extremely wide sweep limits that realizes wavelength (for example, from 1260 nanometers (nm) to 1640 nanometers), and keeps enough narrow frequency range simultaneously.When strengthening OSNR, should not undermine wavelength scanning range.When strengthening wavelength scanning range, should not undermine OSNR.Actual challenge is to realize the higher OSNR and the wavelength of broad simultaneously.

Known FP optical filter OSA owing to the FSR of this optical filter (also can under the non-overlapping situation by tuning in abutting connection with the spectrum interval (spectralseparation) between FP rank (order) (light step)) limited wavelength scanning range arranged.Long (cavity length) is inversely proportional in the chamber of FSR and FP optical filter.Long by reducing the chamber, the FP optical filter can have great FSR.Long by increasing the chamber, the FP optical filter can have minimum FSR.The FSR of FP optical filter also is directly proportional with the BW of this optical filter and the mathematical product of accuracy thereof.For identical precision value, by increase the chamber long and thereby reduce FSR, can make FP optical filter, thereby splendid spectrum resolution degree is provided with 3 decibels of extremely narrow BW.If it is less that BW becomes, it is bigger that accuracy need become, so that keep identical FSR.For the same accuracy value of FP optical filter, FSR is bigger, and then BW is bigger.This kind situation does not wish to see in many application, and this is that the spectrum resolution degree is poorer because BW is healed when big.Therefore, when using the FP optical filter with construction OSA, the FSR of FP optical filter will limit the wavelength scanning range of this optical filter.

In many technology status, must carry out accurate OSA, chromatic dispersion (CD), reach polarisation mode dispersion (PMD) measurement.Thereby need use multiple instrument, this may be quite inconvenient at temporary or field position, and this is because it need be carried to these instruments this place, then these instruments individually is connected to local fiber optic network, and individually operate these instruments, so that carry out various measurements.Therefore, with these OSA, CD, and the PMD measurement function to merge to single multi-functional module will be favourable.This kind mode will be not only by (for example reducing common elements, power supply unit) repetition, and save assembly cost in fact, and will open and to be used for the possibility of all these measurements such as the precision components of FP optical filter, thereby the tester usefulness of facilitating cost savings significantly and significantly improving.

Unfortunately, one type of prior art syringe in the past can't be effectively and merge economically and satisfactorily accurate OSA, CD, and PMD measure.For example, one type of prior art syringe can't be used for single FP optical filter all these type of measurements of the gamut (for example, from 1260 nanometer to 1640 nanometers) of optical communications wavelength.For example, still a unsolved technology barrier is: not only need accurately operate this kind FP optical filter by the utmost point in the optical communications wavelength gamut, and need measure and in scan pattern, operate, and measure and operation in step mode (stepping mode) for CD for OSA and PMD.

Therefore, still needing at present can wavelength division multiplexed (Coarse Wavelength Division Multiplexing for DWDM and thick formula; Be called for short CWDM) use and provide and carry out OSA, CD in the wide wave-length coverage of 1260 to 1630 nanometers, and the high-effect and high-accuracy integrated measuring system measured of PMD.Also need to carry out for optical communication full range band this kind system of this alanysis.Especially again needing only single TFPF to be used for the measuring light wavelength can provide this kind system of these functions efficiently.And need again can the wide wave-length coverage of this kind and even the wave-length coverage of further extending in the single TFPF of this kind system of these functions is provided efficiently.

Because the commercial competition pressure that more and more increases, more and more big consumer's expectation and the more and more little chance of carrying out significant product differentiation in market, thereby the solution of finding out these problems is more and more critical.In addition, the more and more high demand of saving cost, improve efficient, improve usefulness and dealing with this type of competitive pressure has more been increased the emergency of the key needs of the solution of finding out these problems.

Seeking the solution of these problems for a long time, but previous development teaching or advise any solution not as yet, thereby be familiar with this operator and baffled by the solution of these problems for a long time.

Summary of the invention

The invention provides a kind of optical signal measurement system.This optical signal measurement system has tunable Fabry-Perot (FP) optical filter, and via the unknown light signal of this tunable FP optical filter scanning.By this FP optical filter of operation in scan pattern, and can measure wavelength, power, OSNR, and the PMD information of unknown signaling.By this FP optical filter of operation in step mode, but and the chromatic dispersion of measuring light signal.

Some embodiment of the present invention have be used for augmenting or replace above-mentioned these towards other towards.Be familiar with this operator and read at the reference accompanying drawing after hereinafter the detailed description, will be easy to understand these towards.

Description of drawings

Fig. 1 is the signal table generation of tunable Fabry-Perot interferometer;

Fig. 2 is light beam in the tunable Fabry-Perot interferometer of describing among Fig. 1 and the vectogram of following electric field;

Fig. 3 is the figure that can be used to the love force function that the transmission of description Fabry-Perot-type optical filter distributes;

Fig. 4 is the optical circuit schematic diagram of full range band spectrum analyzer according to an embodiment of the invention;

Fig. 5 is a plurality of light steps of describing the middle optical filter of Fig. 4, and describes the long scope of telecommunications all-wave is carried out the figure that slitless spectrum is analyzed;

Fig. 6 is according to embodiments of the invention, describes the schematic diagram of optical signal measurement system;

Fig. 7 is the figure that is used for the R function of the fixed analyzer polarisation mode dispersion method of measurement under weak Mode Coupling according to the present invention;

Fig. 8 is the figure that is used for the R function of the fixed analyzer method under the strong mode coupling according to the present invention;

Fig. 9 A is the schematic diagram that the group delay when being presented at the optical fiber of not accepting test is measured;

Fig. 9 B be the test accepted arranged with schematic diagram like Fig. 9 category-A;

Figure 10 describes the measured relative group delay and the figure of the relation between wavelength;

Figure 11 is a figure of describing the relation between chromatic dispersion versus wavelength; And

Figure 12 is the flow chart of optical signal measurement system according to an embodiment of the invention.

Embodiment

In the explanation hereinafter, many specific detail have been addressed, so that provide to thorough understanding of the present invention.Yet, obviously can not have to implement the present invention under the situation of these specific detail.For fear of having blured the present invention, do not disclose some known circuit and system configuration in detail.Similarly, the graphic of embodiment that device is shown is half schematic diagram, and proportionally do not draw, and especially some size is in order to take the clear of demonstration into account, and shows some size enlargedly in graphic.In addition, when disclosing and explanation when having a plurality of embodiment of some common trait,, explanation graphic in order to take into account, and graphic and explanation understood on clear understandable, usually will be with components identical denotational description similar and identical feature mutually.

According to the present invention, disclosed the system that is used for measuring light wavelength and chromatic dispersion.More specifically, we find and have disclosed measuring system accurately, this measuring system unexpectedly is implemented in the accuracy of the remarkable improvement in the extension wavelength scope, can merge to simultaneously spectroanalysis instrument (OSA) based on Fabry-Perot (FP) optical filter, chromatic dispersion (CD), and the triangular web that constitutes of polarisation mode dispersion (PMD) measuring system.The present invention thereby advanced in fact and utilize Fabry-Perot interferometer (Fabry-Perot Interferometer; Be called for short FPI) to carry out optical wavelength scanning, spectrum analysis, chromatic dispersion, and the state of the art of the device measured of polarisation mode dispersion.

Should find: the FP optical filter can be used for scanning in fact wide wave-length coverage, keep enough narrow frequency range (BW) simultaneously, thereby kept excellent spectrum resolution degree greater than the own free spectral range (FSR) of FP optical filter.

The present invention with single FPI be used for all three kinds of OSA, CD, and the overall with measured of PMD frequently and between frequency band (inter-band) multi-wavelength measure.In this regard, should find: can utilize single tunable FP optical filter to implement to have the full range band OSA of 380 nanometers or bigger wavelength scanning range.In one embodiment, this FP optical filter has the FSR of about 180 nanometers and less than 3 decibels of BW (wave-length coverage is between 1460 nanometers and 1650 nanometers) of 80 micromicrons (80pm).In another wave-length coverage of about 1260 nanometer to 1470 nanometers, FSR is a little little.To define clearly band pass filter (Band Pass Filter then; Be called for short BPF) be used for making a plurality of light steps of this FP optical filter can scan extremely wide wave-length coverage, for example, from 1260 nanometer to 1640 nanometers, this wave-length coverage has contained such as O, E, S, C, and the full telecom wavelengths frequency band of L frequency band.Isolation (isolation) on BPF is decided, and the optical signal isolation between different frequency bands can be greater than 45 decibels.The OSA based on the FP optical filter among this embodiment has then much larger than the wavelength scanning range of the FSR of this FP optical filter.

See also Fig. 1 now, be used as the tunable FPI (100) of the tunable FP optical filter (TFPF) (402) of full range band OSA (400) in (Fig. 4) (not shown, but see also Fig. 4) shown in the figure in the present invention.Tunable FPI (100) has mirror (102) and (104) that are defined at wherein and have partial reflection.Mirror (102) and (104) are separated such as the gap (gap) of chamber (106), and to insert this chamber (106) such as suitable dielectric media such as air, glass.Light (108) enters tunable FPI (100), by tunable FPI (100), leaves tunable FPI (100) then, becomes the light (110) through transmission and optically filtering.

See also Fig. 2 now, vectogram shown in the figure (200) is in order to illustrate incident, reflection, to reach transmitted light beam and the interaction of following electric field and analysis in having the FP optical filter of air gap.The incident electric field R of light (108) _oAt coefficient r _oDown by mirror (102) partial reflection (" being reflected out " chamber (106)), and at coefficient t _iLower part transmission ((106) " interior transmission ") in the chamber.Transmission electric field in chamber (106) is at coefficient t _iWhen transmiting chamber (106) via mirror (104) down, this transmission electric field postpones and multiply by coefficient t behind mirror (104) _oWhen meeting following equation, from the reflection ray R of mirror (102) ₁, R ₂, and R ₃Deng will experiencing the maximal destruction interference, and from the transmitted ray T of mirror (104) ₁, T ₂, and T ₃Deng experiencing maximum constructive enhancing:

$\frac{2\mathrm{\πnL}}{\mathrm{\λ}}=\mathrm{m\π},---\left(1\right)$

Wherein: m is any greater than 0 integer,

L (seeing also Fig. 2) be resonant cavity () length for example, chamber (106),

N is the refractive index of the medium in the resonant cavity, and

λ is the wavelength of light signal and thereby also is the wavelength of transmitted light wave.

See also Fig. 3 now, can be used to describe the figure (300) of the love force function (Airy Function) that the transmission of FP optical filter distributes shown in the figure:

$A\left(\mathrm{\λ}\right)=\frac{I_0}{1+{\left(\frac{2F}{\mathrm{\π}}\sin \frac{2\mathrm{\πnL}}{\mathrm{\λ}}\right)}^2},---\left(2\right)$

Wherein: I ₀Be the peak transmission luminous intensity,

F is the accuracy of FP optical filter, and

λ is the wavelength of light wave.

Following equation is set up the resonance frequency f of tunable FPI (100) _m:

$f_n=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A200780002169E00311.png,A200780002169E00331.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{Ln}}m---\left(3\right)$

Mode spacing (mode spacing) is defined as the free spectral range (FSR) (302) of tunable FPI (100).With regard to the frequency f of light wave, its FSR (302) as shown in the formula:

$\mathrm{FSR}\left(f\right)=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A200780002169E00311.png,A200780002169E00331.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{Ln}}---\left(4\right)$

With regard to the wavelength X of light wave, its FSR (302) as shown in the formula:

$\mathrm{FSR}\left(\mathrm{\&lambda;}\right)=\frac{{\mathrm{\&lambda;}}^2}{2\mathrm{Ln}}---\left(5\right)$

For for the FP optical filter of the FSR with about 180 nanometers (302) in 1500 nano-area, grow up and be about 12.5 microns in the chamber.

The BW of tunable FPI (100) is defined as full width at half maximum (Full Width at HalfMaximum; Be called for short FWHM).Define BW (hertz) by following formula:

$\mathrm{BW}=\frac{1-\mathrm{<figure-callout\; id="2"\; label="r\; r\; c"\; filenames="A200780002169E00311.png,A200780002169E00331.png"\; state="\{\{state\}\}">r</figure-callout>}}{\sqrt{r}}\frac{c}{}\frac{}{2\mathrm{\&pi;nL}}---\left(6\right)$

Wherein: r is the reflection ratio of optical filter mirror,

C is a light speed in a vacuum,

N is the refractive index of the medium in the optical filter chamber, and

L is the length in the chamber (for example, chamber (106)) of optical filter.

When BW and mode spacing (for example, FSR (302)) are correlated with, can produce accuracy F:

$F=\frac{\mathrm{FSR}}{\mathrm{BW}}=\frac{\mathrm{\&pi;}\sqrt{r}}{1-r}---\left(7\right)$

Can try to achieve the approximation of liking force function A (λ) by following Lao Lunzi distribution (Lorentzian distribution):

$L\left(f\right)=\frac{I_0}{1+4{\left(\frac{f-{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="A200780002169E00311.png,A200780002169E00331.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}{\mathrm{BW}}\right)}^2},(\mathrm{for}\frac{f-{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="A200780002169E00311.png,A200780002169E00331.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}{\mathrm{FSR}}<<1)---\left(8\right)$

Wherein: f is the transmitted light wave frequency,

f ₀Be the peak transmission frequency, and

FSR is the free spectral range of FP optical filter.

3 decibels of frequency ranges that Lao Lunzi distributes are identical with 3 decibels of frequency ranges of FP optical filter.

Cutting apart for multiplexed (DWDM) use for the dense wavelength in the optical fiber communication, is in the scope of tens of micromicrons (picometer) to the requirement of optical filter BW.Among the FP optical filter OSA embodiment formerly, the wavelength scanning range of FP optical filter OSA is to be slightly less than its FSR.

Yet, as institute's teaching in this specification, should find: can carry out the FSR (302) of required scanning simultaneously via using several to be configured to simultaneously, and overcome these technology barriers.Thereby can be by several FSR are serially connected, and safeguard and use at commercial FSR that gears to actual circumstances and BW.

According to one embodiment of the invention, and see also Fig. 4 now, the optical circuit figure of the full range band OSA (400) of the tunable optical filter of employing such as TFPF (402) shown in the figure.It is long to drive the chamber of the TFPF (402) that uses among the full range band OSA (400) by PZT (piezoelectric transducer) (piezoelectric transducer) (not shown) traditionally, and by controller/analyzer (406) via suitable numerical digit to analog converter (Digital-to-Analog Converter; Abbreviation DAC) circuit (404) is controlled this PZT (piezoelectric transducer).

According to the equation in the preamble (1), the resonance optical wavelength of TFPF (402) is the function of the long L in its chamber (Fig. 2).Yet equation (1) also illustrates: under identical chamber length, each other a plurality of optical wavelength on different light step m can resonate simultaneously.The FSR (302) of TFPF (402) has defined the maximum wavelength scope that optical filter can scan under the interference that is not subjected to from the signal of its contiguous light step.Shown in the previous FSR example of FP optical filter, thereby extremely limited wave-length coverage based on the existing OSA of FP optical filter has been described.

The present invention defines BPF clearly by utilization and a plurality of light steps of TFPF (402) is scanned different wavelength bands simultaneously, thereby has overcome these restrictions.In one embodiment, the TFPF (402) of full range band OSA (400) has the FSR (302) (in the scope of 1550 nanometers) of about 180 nanometers and 3 decibels of frequency ranges (BW) of about 50 micromicrons.Adopting and under the situation of the BPF that hereinafter is described in more detail, a plurality of light steps of TFPF (402) can be used for scan simultaneously different wavelength bands.Thereby full range band OSA (400) can be used for scanning much larger than the wave-length coverage of the FSR (302) of TFPF (402), for example, from 1260 nanometer to 1640 nanometers, this wave-length coverage has contained the long frequency band of all-wave that telecommunications is used (O, E, S, C, reach the L frequency band).The present invention thereby utilize single FP optical filter and OSA is used for telecommunications full range band uses.

In one embodiment, full range band OSA (400) contains wavelength reference portion (arm) (408), wherein defines light source (410) and optical filter (412).Light source (410) be centre wavelength such as the wideband LED that is approximately 1550 nanometers, and controller/analyzer (406) is controlled light source (410) via driver (414).Optical filter (412) comprises the long FPI (416) of lock chamber, and this FPI (416) has the FSR of about 100GHz (800 micromicron) and the BW of about 80 micromicrons.FPI (416) and bragg grating (Fiber Bragg Grating that lock chamber is long; Be called for short FBG) (for example, having the FBG (418) of 1 nanometer BW) merging, to intercept its resonance peak value in about 1550 nanometers.Have the wavelength reference portion (408) of long FPI (416) of lock chamber and FBG (418) thereby constituted wavelength reference system with micromicron accuracy.Thermistor (thermistor) (420) offers controller/analyzer (406) with the temperature correction information relevant with optical filter (412).

The long FPI (416) of lock chamber is the long FPI of lock chamber that has such as the fixedly FSR of 100GHz.FBG (418) has less times greater than the BW of the BW of the resonance peak of the long FPI (416) of lock chamber.FBG (418) has indenture (notching) position of defining in advance for a resonance peak value that intercepts the long FPI (416) of lock chamber.The long FPI (416) of led light source (410), lock chamber, and this kind merging of FBG (418) then can be provided at the accurate wavelength reference that has in the wave-length coverage between 1460 nanometer to 1650 nanometers less than the accuracy of 1 micromicron.

Full range band OSA (400) also contains optical detection portion (422), wherein defines TFPF (402) and DAC circuit (404).In addition, optical detection portion (422) have BPF (424), (426), and (428), No. three optical splitters (three-way splitter) (430), detector (434), (436), and (438) and be defined in wherein such as simulating to digital converter (Analog-to-Digital Converter; Abbreviation ADC) circuit of (440).BPF (428) and detector (434) have defined such as first detection channels (442) that is used for telecommunications O frequency band.BPF (426) and detector (436) have defined such as second detection channels (444) that is used for telecommunications E frequency band.BPF (424) and detector (438) have defined such as being used for telecommunications S, C, and the 3rd detection channels (446) of L (" S-C-L ＂) frequency band.

First, second, and the 3rd detection channels (442), (444), and the output of (446) be connected respectively to ADC (440), and ADC (440) is processed into the numerical digit form with these outputs, and each other data is passed on (forward) to controller/analyzer (406).Optical detection portion (422) thereby be configured for the wave-length coverage of scanning greater than the FSR (302) of TFPF (402), and detection channels (442), (444), and (446) be configured for simultaneously and individually survey each other a plurality of light step by the wavelength of TFPF (402) scanner uni optically filtering.

Unknown light signal such as wavelength division multiplexed (WDM) signal is provided in the input (448) of full range band OSA (400), has been connected to optical switch (452) and import (448).Before full range band OSA (400) the scanning unknown WDM signal from input (448), optical switch (452) is set to the wavelength reference portion (408) that is configured to wavelength reference and calibration information are offered TFPF (402).Scan this wavelength reference and calibration information then, and the result is stored in controller/analyzer (406).

Then optical switch (452) is set for the unknown WDM signal that is connected in the input (448), scan this unknown WDM signal from input (448) this moment once again, makes the TFPF (402) will be by its unknown light signal optically filtering.Then with will in the mode of hereinafter explanation analyze from first, second, and the 3rd detection channels (442), (444), and result's output of (446) so that full range band spectrum analysis from this unknown WDM signal of input (448) is provided in output (454).

In order to survey previously described three telecom band, in one embodiment, BPF (424), (426), and (428) have following value:

BPF (424):, stop other wavelength by the wavelength to about 1650 nanometers from about 1457 nanometers;

BPF (426):, stop other wavelength by the wavelength to about 1490 nanometers from about 1345 nanometers;

BPF (428):, stop other wavelength by the wavelength to about 1378 nanometers from about 1260 nanometers.

Thereby produce and defined the wavelength detection scope (512) (seeing also Fig. 5) of 1457 nanometer to 1650 nanometers of the wavelength detection scope (510) (seeing also Fig. 5) of 1345 nanometer to 1490 nanometers of wavelength detection scope (508) (seeing also Fig. 5), second detection channels (444) of 1260 nanometer to 1378 nanometers of first detection channels (442) and the 3rd detection channels (446).

In another embodiment, BPF (424), (426), and the frequency band that passes through of (428) can be slightly different.For example:

BPF (424):, stop other wavelength by the wavelength to about 1650 nanometers from about 1465 nanometers;

BPF (426):, stop other wavelength by the wavelength to about 1480 nanometers from about 1350 nanometers;

BPF (428):, stop other wavelength by the wavelength to about 1370 nanometers from about 1260 nanometers.

Pass through frequency band to (pair) thereby to have such as width be that overlapping some of 10 nanometer to 30 nanometers is overlapping in abutting connection with BPF.Yet, though found this kind overlapping be favourable, this overlapping should be wide and make from the signal of different light steps and can't be distinguished.

See also Fig. 5 now, TFPF shown in the figure (402) (Fig. 4) a plurality of light steps and the present invention in the figure (500) that is used for the long scope of the telecommunications all-wave of 1260 nanometer to 1640 nanometers is carried out the system of seamless (seamless) OSA scanning that discloses.(for example, BPF (424), (426), and (428) (Fig. 4), so that provide suitable stopping to the contiguous light step of m light step (that is, a m+1 and m-1 light step) clearly to define various optical filters in previously described mode.Therefore, with reference among the described embodiment of Fig. 4, the BPF (424) that is used for the S-C-L frequency band has the passage that passes through from about 1457 nanometer to 1650 nanometers (wavelength detection scope (512)) in preamble, and has stopped the signal from other wavelength bands.The BPF (426) that is used for the E frequency band has the passage that passes through from about 1345 nanometer to 1490 nanometers (wavelength detection scope (510)), and has stopped the signal from other wavelength bands.The BPF (428) that is used for the O frequency band has the passage that passes through from about 1260 nanometer to 1378 nanometers (wavelength detection scope (508)), and has stopped the signal from other wavelength bands.

In operation, when process along with the time, at the different wavelength components of unknown WDM signal of input (448), and during tuning constantly TFPF (402), DAC circuit (404) is (Fig. 4) long in the chamber of the pattern of looking around (sweeping mode) following control TFPF (402), so that define scanning.In Fig. 5, Y-axis (" DAC → TFPF ") is the reading (with the expression of counting) that DAC circuit (404) is input to TFPF (402), and this reading is directly proportional with the voltage that is used for controlling PZT (piezoelectric transducer) (PZT) (not shown) among the TFPF (402).X-axis is the resonant wavelength λ of TFPF (402), and this resonant wavelength λ is long corresponding to the instant chamber of TFPF (402).As known in this technology, this chamber length is the function of the control voltage of PZT (piezoelectric transducer) as mentioned before.

In Fig. 5, (" O-band-3 ", " O-band-2 ", " E-band-2 ", " S-C-L-band-2 ", " E-band-1 " and " S-C-L-band-1 " illustrate the resonant wavelength of TFPF (402) and how to respond from the control of DAC circuit (404) and to count for different light steps six curves.These six curves can be combined into the curve of three extensions, wherein the O-band-3 curve is the first extension curve (502), O-band-2, E-band-2, and the S-C-L-band-2 curve be second to extend curve (504), and E-band-1 and S-C-L-band-1 curve are the 3rd to extend curve (506).These three extension curves (502), (504), (506) illustrate the λ of TFPF (402) _M+1, λ _m, and λ _M-1Three different light steps out of the ordinary.

For example, when DAC circuit (404) is sent out about 1190 count (only on X-axis), the signal on about 1260 nanometers and about 1455 nanometers will begin resonance simultaneously.Yet the detector of O frequency band (434) (Fig. 4) will only be seen the signal of 1260 nanometers in its wavelength detection scope (508).This detector stops because of first detection channels (442) BPF's (428) (Fig. 4), and can't see 1455 nanowire signals outside its wavelength detection scope (508).

When increasing during the input of DAC circuit (404) is looked around (sweep) in spectrum analysis, the resonant wavelength of TFPF (402) increases, and this program lasts till till 1378 nanometers that this moment, the BPF (428) of O frequency band stopped the signal of O band detector (434).Yet the detector of E frequency band (436) (Fig. 4) begins to collect data on about 1345 nanometers.Signal between 1345 nanometers and 1378 nanometers is surveyed by detector (434) and (436) simultaneously, so that provide crossing over the seamless scanning of O and E frequency band.

The detector of E frequency band (436) continues to collect data, and till 1490 nanometers, this moment, the BPF (426) of E frequency band stopped the signal of E band detector (436).The detector of S-C-L frequency band (438) (Fig. 4) begins to collect data on about 1475 nanometers.Zone between 1457 nanometers and 1490 nanometers reaches (438) by E frequency band and S-C-L band detector (436), and both are surveyed, so that provide crossing over the seamless scanning of E and S-C-L frequency band.

In one embodiment, DAC circuit (404) is looked around 32768 points from 0.Equation (1) and Fig. 5 illustrate: each wavelength can be at different light step low-resonances.For example, the signal on 1260 nanometers will resonate on two that are approximately 1190 and 22220 different DAC values.Signal on 1460 nanometers will be approximately resonance on two other DAC value of 2190 and 26110.For the O frequency band, can ignore then and be higher than 17000 any DAC values of counting (corresponding to about 1380 nanometers), to avoid because of obscuring that these a plurality of light steps cause.Similarly, for the E frequency band, can ignore then and be lower than 12000 any DAC values of counting (corresponding to about 1330 nanometers), obscure to avoid this kind.Therefore, for whole O and E frequency band, do not use these DAC points on the O-band-3 curve that produces because of m+1 light step.In order to simplify, numeral " 3 " is used to represent m+1 light step.For whole O and E frequency band, only use the O-band-2 curve that produces because of m light step and those DAC points on the E-band-2 curve.Numeral " 2 " still is used to represent m light step.For S, C, and the L frequency band for, only use those DAC points on the S-C-L-band-1 curve that produces because of m-1 light step.In order to simplify, numeral " 1 " is used to represent m-1 light step.

As teachings of the present invention, thereby find: use OSA based on the FP optical filter, can realize to the long frequency band of telecommunication all-wave (for example, from 1260 nanometer to 1650 nanometers) seamless scanning, wherein the FSR of this FP optical filter much smaller than total wavelength across scope.Define as equation (6), under the situation of the BW that does not sacrifice this optical filter, realize the sweep limits of this kind broadness.And, must use the optical filter that has greater than the big FSR of total sweep limits in prior art that is used for broad wavelength scanning range and design.Yet for identical accuracy, FSR is bigger, and the BW of optical filter is bigger, thereby the spectrum resolution degree will be poorer.This promptly means: previous design realizes bigger sweep limits by the mode of sacrificing the spectrum resolution.Yet the present invention realizes bigger OSA sweep limits (that is, realizes bigger " FSR (netFSR) only "), keeps the identical FSR of each light step simultaneously.Therefore, kept the original BW of each light step of FP optical filter, thereby kept the high spectrum resolution degree (being approximately the spectrum resolution degree of the intrinsic FSR of optical filter) of optical filter in whole OSA sweep limits.

Provided by the present invention another significantly improvement be to scan a plurality of FSR or light step simultaneously, thereby the sweep speed when once only scanning single FSR is when comparing, scanning imaging system of the present invention significantly quickens.

Therefore, several light steps of TFPF (402) are separated fully, thereby can simultaneously but still clearly and individually survey and analyze multistage light signal.Therefore, this full range band OSA can be successfully and is advantageously used single FP optical filter such as TFPF (402), promptly to scan much larger than broad many wave-length coverages of the FSR (302) of this FP optical filter itself.

The isolation that these BPF of the described embodiment of preamble provide is approximately 40 decibels, thereby guarantees than (OSNR) that for the light signal noise 40 decibels measuring range is arranged.According to announcement of the present invention, this technology is had the general knowledge, and the person can understand now: under preferable isolation, and the present invention even better OSNR dynamic range can be provided.

See also Fig. 6 now, the schematic diagram of optical signal measurement system (600) according to an embodiment of the invention shown in the figure.Many assemblies of optical signal measurement system (600) and function class are similar to full range band OSA (400) those assemblies and function (Fig. 4), thereby will be with these assemblies of components identical symbolic representation and function.

Yet full range band OSA (400) and be according to the significant difference between optical signal measurement system of the present invention (600): optical signal measurement system (600) is not only carried out full range band OSA, and carries out full range band CD extraly and full range band PMD measures.And unexpectedly find: can only use single FPI (that is, TFPF (402)) and three kinds of important measurement functions (OSA, CD, and PMD) are merged to single optical signal measurement system (600).This is more to make us surprised and beyond thought, this is because OSA and PMD measurements are by continuing to look around the continuous measurement that unknown input signal is carried out, and CD measurements is to measure the step mode of the unknown input signal on the wavelength location specific, that separate, the interval or stepping (rather than scan-type) measurement that mode is carried out by a kind of in the time durations of setting.

Because be not to look around the CD measured value constantly, so must implement a kind of very different and formerly be the control forms of difficulty extremely to measuring optical filter.Especially be difficult to utilize the FP optical filter to implement this kind control, thereby cause other optical filter configurations of preference such as FBG in CD measures.Yet, find and teaching as the present invention, can be economical and only use single FPI efficiently and merge all three kinds of measurement functions (OSA, CD, and PMD), and can realize the measurement correctness and the usefulness of all three kinds of measurement functions, and a plurality of independently measuring systems that are better than various prior aries consume the result that higher cost just can obtain.

How main difficulty during the known previous CD that DAC is used for controlling FPI (for example, DAC circuit (404) is used for controlling TFPF (402)) measures is set to the value that can just in time obtain required wavelength from TFPF (402) with DAC circuit (404) just.The previous known very high stability that can't provide is provided this kind mode.For example, when the value of the DAC circuit (404) that will be used for a stepping measurement was changed into the value that is used for a time stepping measurement, DAC circuit (404) will correspondingly step to TFPF (402) and be used for an inferior wavelength is carried out the position of optically filtering.Yet TFPF (402) is a kind of physical unit, thereby can't be converted to an accurate time value at once.Or rather, the actual physics wavelength set of TFPF (402) may be drifted about a little, perhaps may drift about constantly, makes its correctness that is difficult to keep TFPF (402) be used to guarantee the correctness of measuring.

Therefore, in the present invention, the stability of optical signal measurement system (600), accurate control, and the accuracy calibration be the new key element and the feature of strange preciousness.Therefore, after optical signal measurement system (600) itself has been described, calibration and operation will be described hereinafter.

Can learn that by consulting Fig. 6 optical signal measurement system (600) comprises in the preamble (Fig. 4) the described most assembly with reference to full range band OSA (400), and thereby utilize the long band capability of all-wave of full range band OSA (400) and TFPF (402) wherein.But in addition, as mentioned before, TFPF (402) is further used in optical signal measurement system (600), to carry out the chromatic dispersion measurement such as CD and PMD measurement of optical fiber.Such as the single FP optical filter of TFPF (402) thereby carry out the long frequency band of all-wave (for example, contain O, E, S, C, and 1260 nanometer to 1640 nanometers of L frequency band) OSA, CD, and PMD analysis.

Optical signal measurement system (600) comprises two 1 * 3 optical switches, that is, first optical switch (602) and second optical switch (604).Each port in three ports (port) of first optical switch (602) be connected respectively to be used for O, E, and the light path out of the ordinary of S-C-L frequency band first, second, and the 3rd detection channels (442), (444), and (446).Each port in three ports of second optical switch (604) be connected respectively to have OSA detector (606) respectively, PMD detector (608), and OSA, the PMD of CD detector (610), and CD detection channels (be denoted as respectively " OSA ", " PMD ", and " CD ").

This OSA detection channels is used for OSA and measures, and comprise OSA detector (606), OSA detector (606) is sent to ADC (440) with its result of detection, ADC (440) will be processed into the numerical digit form from the output of OSA detector (606), and each other data is transferred to controller/analyzer (406).

This PMD detection channels is used for PMD to be measured, and comprises PMD detector (608) and polarizer (polarizer) (612).Polarizer (612) makes this light signal polarization from second optical switch (604) receiving optical signals, and it is transferred to PMD detector (608).PMD detector (608) is sent to ADC (440) with its result of detection, and ADC (440) will be processed into the numerical digit form from the output of PMD detector (608), and each other data is transferred to controller/analyzer (406).

This CD detection channels is used for CD and measures, and be configured in CD daughter board (daughter board) (614) in one embodiment, this CD daughter board (614) comprises two FBG (616), clock pulse (618) and time to digital transducer (Time-to-Digital Converter; Be called for short TDC) (620).CD daughter board (614) is handled this light signal from second optical switch (604) receiving optical signals in the mode that will further specify in this specification, and each other dateout is transferred to controller/analyzer (406).

For full range band OSA measures, the operation of optical signal measurement system (600) as mentioned before, wherein second optical switch (604) is set to the OSA passage that contains OSA detector (606).Under scan pattern, operate TFPF (402), wherein first optical switch (602) be operated and the O, the E that select respectively to be scanned, and the S-C-L frequency band various first, second, and the 3rd detection channels (442), (444), and (446).

For full range band PMD measures, also by operating TFPF (402) in the scan pattern, and carry out the operation of optical signal measurement system (600), but second optical switch (604) is set to the PMD passage that contains PMD detector (608).Operate first optical switch (602) in a similar fashion, so as the O, the E that select respectively to be scanned, and the S-C-L frequency band various first, second, and the 3rd detection channels (442), (444), and (446).

Be called as " fixed analyzer method " based on PMD measurement such as the tunable optical filter configuration that discloses among the present invention.Finish the PMD scanning that continues to look around, and the power trace that controller/analyzer (406) will be received by the PMD detector (608) in the PMD path is P _p(λ).Similarly, controller/analyzer (406) power trace that will be received by the OSA detector (606) in the OSA path is P _Tot(λ).Then with the following formula rated output than R (λ) (be called as " R (λ) function ", or be called simply " R function ").

$R\left(\mathrm{\&lambda;}\right)=\frac{P_p\left(\mathrm{\&lambda;}\right)}{P_{\mathrm{Tot}}\left(\mathrm{\&lambda;}\right)}---\left(9\right)$

Two kinds of methods from measured R (λ) function calculation PMD are arranged, for example, extreme value counting (extrema counting) and Fourier transform.If use the extreme value method of counting, then should be from λ ₁Minimum wavelength to λ ₂The wavelength spacing (interval) of some equal intervals of maximum wavelength on obtain this R (λ) function.N is the number of the extreme value (maximum and minimum value) in this scope.Perhaps, can define wave-length coverage again, make λ ₁And λ ₂Consistent with extreme value, in this kind situation, N is that extreme value (comprises λ ₁And λ ₂) number subtract one.PMD value＜Δ τ〉formula be:

$<\mathrm{\&Delta;\&tau;}>=\frac{\mathrm{kN}{\mathrm{\&lambda;}}_1{\mathrm{\&lambda;}}_2}{2c({\mathrm{\&lambda;}}_2-{\mathrm{\&lambda;}}_1)}---\left(10\right)$

Wherein: c is a light speed in a vacuum, and

K is the Mode Coupling factor (mode-coupling factor), and k does not equal 1.0 when having the strong mode coupling, and equals 0.82 under the restriction of strong mode coupling.

See also Fig. 7 now, shown in the figure according to the present invention and the figure (700) of the power ratio function R (λ) of the fixed analyzer method under weak Mode Coupling.

See also Fig. 8 now, shown in the figure according to the present invention and the figure (800) of the power ratio function R (λ) of the fixed analyzer method under strong mode coupling.

For full range band CD measures, by operation TFP F (402) in the step mode, and the operation of execution optical signal measurement system (600), wherein second optical switch (604) is set to the CD passage that contains CD detector (610).Operate first optical switch (602) in required mode, so as the O, the E that select respectively to be scanned, and the S-C-L frequency band various first, second, and the 3rd detection channels (442), (444), and (446).

More specifically, in one embodiment, use " time delay method ", so that the relative time of measuring on the wavelength of each different stepping postpones based on the CD measurement of TFPF (402) configuration.In the measurement of the relative group delay (groupdelay) that the optical fiber by known length experiences, reason out CD by various wavelength then.By surveying, record, and handle the delay that the pulse wave (pulse) of each wavelength in the wavelength of various steppings is experienced, and in time domain, measure this group delay.

See also Fig. 9 A and 9B now, how to measure schematic diagram out of the ordinary (900) and (902) of group delay shown in the figure.In Fig. 9 A, external LED (904) contains the wideband light-emitting diode, and this wideband light-emitting diode is driven by pulse (pulsar), and launches the long light pulse wave (906) of 500 psecs (ps).If do not accept the optical fiber of test, then only by TFPF (402), TFPF's pulse wave (906) (402) works under step mode, and produces a series of pulse wave (908), one pulse wave (908) is wherein arranged on each wavelength X, and these pulse waves (908) are separated by postponing τ.Shown in Fig. 9 B, if the optical fiber (910) of the test accepted is arranged, then when pulse wave (906) passed through this optical fiber, chromatic dispersion was such as τ ' with the deferred update between the pulse wave (912) of series.Time resolution detecting function in the CD daughter board (614) is measured this new delay.Difference τ '-τ is group delay, and can reason out chromatic dispersion from this group delay.Adopt photon counting to survey (photon counting detection), so that obtain required high sensitivity and high temporal analytical density.Knownly in the paper of delivering in " LIFGTWAVE, August 2000 " " Photon-countingtechniques for fiber measurements ", this kind photon counting is being described such as Bruno Huttner and Jurgen Brendel.

Please consult Fig. 6 again, in order to operate TFPF (402) in step mode, other light signals that CD daughter board (614) and unknown light signal or acceptance are measured are synchronous in time.The light signal of transmit to accept measuring from optical switch (452) via two-way optical splitter (622) (for example, the signal on the light signal incoming line (628)), and realize above-mentioned synchronously.The light signal that two-way optical splitter (622) will accept to measure is sent to the clock pulse (618) on TFPF (402) and the CD daughter board (614).Clock pulse (618) then with this signal Synchronization, and this signal is and the identical light signal of light signal that is sent to TFPF (402) from two-way optical splitter (622) simultaneously.

In step mode, operate among the TFPF (402), during measuring, TFPF (402) is stabilized on each selecteed accurate wavelength of stepping of each separation.Before each CD measures, make optical switch (452) be directed to wavelength reference or calibration portion (408).TFPF (402) works under the pattern of looking around.Optical switch (604) is directed to OSA portion.TFPF (402) looks around calibration spectrum, and this calibration spectrum has because of a plurality of resonant wavelength peak values that FPI (416) causes, reaches and omit peak value.Because this omits the known location of peak value, and know the wavelength location of these peak values.Thereby count relation between (value of DAC circuit (404)) and wavelength location of the DAC that has set up driving TFPF (402).Then optical switch (452) is directed to light signal input part (448), and optical switch (604) is directed to CD portion.The TFPF (402) that is now just working under step mode is set to and is used for the first wavelength location λ that CD measures ₁Survey and recording wavelength λ by time resolution probe unit (614) (that is, CD daughter board (614)) ₁The relative arrival sequential of this pulse wave.Then, begin another time calibration and measuring period.Optical switch (452) is directed to wavelength calibration portion (408), and carries out calibration once again.TFPF (402) is tuned to and is used for the second wavelength location λ that CD measures ₂Survey and recording wavelength λ by time resolution detection portion (614) ₂The relative arrival sequential of this pulse wave.The rest may be inferred, till the relative arrival sequential of the pulse wave of having measured last wavelength.

See also Figure 10 now, the measured relative group delay shown in the figure and an example (1000) of the relational graph between wavelength.Relation between group delay and wavelength in many cases, can second order polynomial be described.

See also Figure 11 now, the example of the relational graph shown in the figure between chromatic dispersion versus wavelength (1100).With group delay the mode of the differential of wavelength is calculated chromatic dispersion.

In one embodiment, CD detector (610) (Fig. 6) contains avalanche-type photo-detector (the Avalanche Photo Detector that is configured to photon is count down to the degree of individual photons downwards; Be called for short APD).For CD measured, the present invention can carry out single photon counting then.The ability of this kind single-photon counting is the advantage of essence, and this is because several optically filtering levels after and at CD detector (610) some light signal before may be (seeing also Huttner and Brendel paper that preamble is quoted) a little less than extremely.

In overall operation, optionally and first alignment light Signal Measurement System (600).In some cases, calibration will be the periodicity calibration in the laboratory environment (or similar site) that can use the suitable tunable formula calibration laser of known and common wideband source.Can carry out this kind calibration such as optical alignment signal (624) from calibration reference (626).Calibration reference (626) can be such as by precalibrated tunable laser.

In one embodiment, via TFPF (402) (for example, via optical switch (452)) transmit light source with known wavelength, and set up the correlation of DAC circuit (404) value of the signal that makes TFPF (402) survey this wavelength, and carry out calibration to optical signal measurement system (600).Can repeat this program for required or spendable many wavelength then, so as to set up DAC circuit (404) value, corresponding TFPF (402) position, with corresponding wavelength between relation.This calibration procedure is for each light step of several TFPF (402) light step that is detected in the optical signal measurement system (600) and produce calibration correlation one to one between DAC circuit (404) value and corresponding wavelength value.Should find: through calibration and these correlations directly related with the light step a plurality of out of the ordinary of the wavelength that is scanned by TFPF (402) is stable, and can during for a long time and in multiple use and the field conditions (for example, situation such as all temps, power supply supply voltage), use these correlations reliably.

For The field, the single tuning measurement of existing (" in the scene ") calibration can be enough.The tuning measurement of the calibration that this kind is single can determine the skew (offset) of existing job status simply.This skew can be applied to complete previous (for example, on laboratory or workbench) calibration then, this calibration can be used for full range band spectrum scope together with the existing skew of this field calibration then.(workbench) calibration that can this is previous is stored in such as in controller/analyzer (406).

In another embodiment, can will calibrate correlation in a similar manner prior to early the time and capture (for example) in the table of comparisons, and this table of comparisons will be stored in such as in controller/analyzer (406) as the part of laboratory or workbench calibration procedure.Then, following passing through with reference to this table of comparisons, can determine: for any specific DAC value, the wavelength which is detected will be such as in first detection channels (442), the wavelength which is detected will be in second detection channels (444), and the wavelength which is detected will be in the 3rd detection channels (446).In one embodiment, this table of comparisons is called as " calibration mapping table ".

Another calibration procedure can be used for for the specific operation that may soon occur now and environment condition and produce being used for the tuning of this calibration mapping table.For example, may need to adapt to be different from present during the original calibrated such as temperature contrast, voltage differences, and the field conditions of humidity difference etc.It should be noted that: these relative wavelength values in this calibration mapping table keep stable each other, and keep its one-to-one correlation under these field conditions.

Yet field conditions may produce DAC skew, makes the DAC value then corresponding on the same group corresponding wavelength not.Therefore, can before this wavelength reference system of use, carry out field calibration earlier.Can the local spendable external calibration reference source that is connected to light signal incoming line (628), or, carry out this field calibration with spendable internal reference source such as wavelength reference portion (408).

Therefore, the spendable field calibration reference source of use such as wavelength reference portion (408), can set up that DAC counts and the reference wavelength in this spendable source between existing instant relation, and in one embodiment, these existing instant relations are stored in second stored in such as controller/analyzer (406) table.Value in this second table has been set up correlation and the contrast between the relevant on-site wavelength value of this original calibrated mapping table and existing actual field DAC and this wavelength reference system.In one embodiment, this second calibration table of comparisons is called as " dynamically mapping table ".

Extra (the 3rd) table also proves useful.For example, in one embodiment, the detection channels that can be fallen into for field calibration light source reference wavelength (for example then, first, second or the 3rd detection channels (442), (444) or (446)) in each wavelength and calculate and produce the tuning of DAC value or skew, and tuning or skew is stored in such as in controller/analyzer (406) with these.In one embodiment, the 3rd offset table is called as " dynamic deflection value table ".

For the unknown wavelength that occurs in the light signal incoming line (628) is carried out scanning, then according to the value in this dynamic deflection table and tuning (compensation) this resulting DAC value of (the unknown) wavelength that is detected, thereby the split-hair measurement that produces the wavelength that is scanned.

More specifically, via light signal incoming line (628) one or more unknown light signals are input to optical signal measurement system (600).Scan these unknown signalings via TFPF (402) then, and when wavelength signals is individually selected by TFPF (402) and detected by the detector that second optical switch (604) is selected, obtain corresponding DAC circuit (404) value of reading.After deduction is counted by the drift of the described correspondence of this dynamic deflection table, utilize this calibration mapping table to reason out DAC circuit (404) the value corresponding accurate wavelength location measured, thereby specified the accurate wavelength of unknown signaling with each.Measure wavelength value then via the correspondence of the unknown light signal of TFPF (402) scanning, and such as these wavelength value being stored in controller/analyzer (406), or in the mode via output (454) transmission data, and specify these wavelength value.

In one embodiment, thereby can in the various device parts of optical signal measurement system (600), carry out the groundwork that scans unknown light signal via tunable optical filter.Decide on applicability the measurement that will carry out, the control that these parts are included in DAC circuit (404) down and the control of the circuit in controller/analyzer (406) TFPF (402) down and also comprises first, second, and the 3rd detection channels (442), (444), reaches (446).Similarly, can carry out the groundwork of measuring by the various device assemblies of optical signal measurement system (600) via the unknown wavelength of optical signal value of tunable optical filter scanning, and decide on the applicability to the measurement that will carry out, these assemblies comprise detector (606), (608), and (610).Similarly, can in the circuit of controller/analyzer (406), reach (or) under its control, carry out the groundwork of specifying the wavelength value in the unknown light signal.

See also Figure 12 now, the flow chart (1200) of optical signal measurement system (1200) according to an embodiment of the invention shown in the figure.System (1200) comprises the following step: in step (1202), provide tunable optical filter; In step (1204), scan unknown light signal via this tunable optical filter; In step (1206), under scan pattern, operate this tunable optical filter at least one measurement in OSA and the PMD measurement, and for CD measure and under step mode operation this tunable optical filter, and measure the wavelength and the dispersion values of this unknown light signal that scans via this tunable optical filter; And in step (1208), specify the wavelength and the dispersion values of this unknown light signal.

Should find: the present invention thereby have is used for the measuring light characteristics of signals many towards.

Of the present invention one towards thereby advanced the spectrum analysis of using tunable FP interferometer, polarisation mode dispersion, and dispersion means, method, and the state of the art of related system in fact.

Of the present invention one mainly towards provided these certain surface of having benefited from and having utilized the FP interferometer to and the very effective and high efficiency OSA-CD-PMD optical signal measurement system of ability.

Another critical surfaces of the present invention is to this kind system that only uses and need single TFPF is provided for it.

Another side is to being: the invention provides accurate measuring system, this measuring system has unexpectedly realized the correctness in the significant improvement of the wave-length coverage of extending, and simultaneously can with based on OSA, the CD of FP optical filter, and the PMD measuring system merge to triangular web.

Another side again of the present invention is to being: the present invention can only use be easy to for three kinds of OSA, CD, and PMD measure and the single TFPF of calibration stably.

Another critical surfaces is to being: can be easy to measure and under the pattern of looking around for OSA and PMD, and measure and under step mode, the utmost point is operated the single TFPF in this single optical signal measurement system exactly for CD.

Another side is to being again: since with all three kinds of OSA, CD, and PMD measure and to merge to single system efficiently, and can assembly, assembling, and manufacturing cost on significant saving and efficient are provided.

Of the present invention one mainly towards thereby be: the invention provides spectroanalysis instrument and frame of reference, this kind system is used for the TFPF of pinpoint accuracy and high correctness a plurality of measurements of optical wavelength of the wave-length coverage of broadness and extension.

Another critical surfaces again of the present invention is to being: the present invention supports valuablely and serves and reduces cost, simplified system, and increase the historical trend of usefulness.

Of the present invention these and other valuable towards thereby the state of technology is advanced to next level at least.

Therefore, should find: optical signal measurement system of the present invention provide spectrum analysis the important and hitherto solution that also never had, ability, and function towards.The system that is provided be clear and definite, cheaply, uncomplicated, multiduty, and effectively, and can be by transforming known technology implementing this kind system, thereby be suitable for making and operating efficiently and economically dynamical optical signal measurement system easily.

Though with reference to specific optimal mode the present invention has been described, should have understood: be familiar with this operator after the explanation of consulting preamble, will be easy to make many variations that substitute, revise, reach.Therefore, the present invention will comprise in the scope that drops on last claims all this type of substitute, revise, and change.Will with illustration and nonrestrictive mode annotate address in this specification preamble or accompanying drawing shown in all the elements.

Claims (12)

1. an optical signal measurement system (1200) comprising:

(1202) tunable optical filter (402) is provided;

Via this tunable optical filter (402) scanning (1204) unknown light signal (628);

By this tunable optical filter (402) of operation, and measure (1206) wavelength and dispersion values via this unknown light signal (628) of this tunable optical filter (402) scanning:

In scan pattern, operate this tunable optical filter at least one measurement in spectroanalysis instrument and the polarisation mode dispersion measurement; And

In step mode, operate this tunable optical filter for chromatic dispersion measurement; And

Specify this wavelength and this dispersion values in (1208) this unknown light signal (628).

2. the system as claimed in claim 1 (1200) wherein, provides (1202) tunable optical filter (402) further to comprise: single Fabry-Perot optical filter (402) is provided.

3. the system as claimed in claim 1 (1200) further comprises: make this tunable optical filter (402) be stabilized in each wavelength of each stepping of this step mode for chromatic dispersion measurement.

4. the system as claimed in claim 1 (1200) wherein, is measured (1206) these dispersion values for chromatic dispersion measurement and is further comprised: measure this unknown light signal (628) with avalanche-type photo-detector (610) in step mode.

5. the system as claimed in claim 1 (1200) further comprises: scan arrogant at least extremely roughly 1640 nanometer wavelength range of 1260 nanometers that cause.

6. the system as claimed in claim 1 (1200) further comprises: by measuring this relative group delay, and then from this chromatic dispersion of differential calculation to wavelength of this relative group delay, and carry out chromatic dispersion measurement.

7. an optical signal measurement system (600) comprising:

Tunable optical filter (402);

Be used for scanning the device (600) of unknown light signal (628) via this tunable optical filter (402);

Be used for measuring the wavelength of this unknown light signal (628) that scans via this tunable optical filter (402) and the device (600) of dispersion values by this tunable optical filter (402) of operation:

In the one scan pattern, operate this tunable optical filter at least one measurement in spectroanalysis instrument and the polarisation mode dispersion measurement; And

In step mode, operate this tunable optical filter for chromatic dispersion measurement; And

Be used to specify this wavelength in this unknown light signal (628) and the circuit (406,440,614) of these dispersion values.

8. system as claimed in claim 7 (600), wherein, this tunable optical filter (402) further comprises single Fabry-Perot optical filter (402).

9. system as claimed in claim 7 (600) further comprises the device (408) of each wavelength of each stepping that is used for making this tunable optical filter (402) be stabilized in this step mode for chromatic dispersion measurement.

10. system as claimed in claim 7 (600) wherein, is used for for chromatic dispersion measurement and further comprises avalanche-type photo-detector (610) at this device (600) that step mode is measured these dispersion values.

11. system as claimed in claim 7 (600), wherein, this tunable optical filter (402) further comprises and is configured for arrogant at least 1260 nanometers that cause of scanning to the tunable optical filter (402) of 1640 nanometer wavelength range roughly.

12. system as claimed in claim 7 (600) further comprises being used for by measuring this relative group delay and from this relative group delay this chromatic dispersion of differential calculation of wavelength being carried out the circuit (406,614) of chromatic dispersion measurement then.

Images