CN101013923A - Analog transmitter using an external cavity laser (ecl) - Google Patents
Analog transmitter using an external cavity laser (ecl) Download PDFInfo
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Abstract
This invention relates to an analog transmitter using an external cavity laser (ECL) in which the second and third distortions are improved by increasing the threshold value of the generation of harmful stimulated Brillouin scattering and increasing and using the inherent property of the ECL. The performance of ECL shows substantial decrease in distortion produced over the specified narrow range of operation temperature. This invention relates to an optical methodm, electronic method, thermology method and/or mechanical method, in which 'distortion DIP' is moved away from mode hop to the stable region of ECL operation or created away from the mode hop in the stable region of the ECL operation. The distortion DIP is either moved to or created in an ECL operation region, in which sufficiently high charp is produced, to reduce SBS. This invention also relates to a transmitters using these corresponding technology and other devices.
Description
The related application cross reference
The application's case according among 35 U.S.C. § 119, § 120, the § 365 one or more advocate on April 2nd, 2004 file an application the 60/558th, No. 927 temporary patent application cases, and filed an application on April 16th, 2004 the 60/562nd, the priority of the 60/638th, No. 679 temporary patent application case that No. 762 temporary patent application cases and on December 23rd, 2004 file an application.For various purposes, the full content of all described temporary patent application cases all is incorporated herein with way of reference.
Technical field
The present invention relates to optical communication field by and large, and more specifically relates to a kind of simulating emitter and outside cavity gas laser that is applicable in the optical communication system.
Background technology
In cable TV (CATV), be used for broadcasting and Narrowcasting (QAM form) and use the two direct modulation profile formula feedback (DFB) laser of the common use of simulating emitter or external modulation source (continuous wave (CW) Distributed Feedback Laser adds an external modulator).This selection depends primarily on application, operation wavelength (being generally 1310 nanometers-nm or 1550nm), scope and optical power levels.Different reflector options had both had advantage usually and had also had shortcoming-be usually directed to several basic problems of analogue transmission.The factor of being considered when assessment reflector option generally includes (for example) in the level of the output place of reflector generation distortion, because of there be (for example erbium-doped fiber amplifier, the distortion deterioration that EDFA) causes and the chromatic dispersion that occurs of filter and/or optical amplifier when signal passes monomode fiber (especially on the 1550nm wavelength).
Wave division multiplexing (WDM) allows to transmit simultaneously a plurality of different wavelength of laser bundles that are in respectively in single strand optical fiber.WDM can be used for all types of optical systems based on optical fiber, comprises base-band digital system, analog broadcasting and Narrowcasting system, reaches the system of transmitting RF on optical fiber.The wavelength channel quantity that increase can be transmitted is simultaneously impelled and has been introduced intensive WDM (DWDM).For example standardization such as International Telecommunication Union has been introduced the standard of dwdm system, wherein except that other data, has stipulated the spacing (being also referred to as ITU grid or standard grid) between the adjacent wavelengths.As an example, I.T.U.G.957 is one and is called the normative document of " ITU-T standard: be used for the equipment relevant with SDH (Synchronous Digital Hierarchy) and the optical interface of system (ITU-T Specification:Optical Interfaces For EquipmentsAnd Systems Relating To The Synchronous Digital Hierarchy) ".
Optical transmitting set adopts the method that suppresses excited Brillouin (Brillouin) scattering (SBS) usually.In brief, SBS is interacted by the nonlinear optical in the monomode fiber-sound to cause.SBS can limit transmission range (being transmission range) and also can limit the maximum luminous power amount that can inject in the optical fiber.Typical SBS inhibition method comprises makes institute's transmission signals to be different from frequency and the form dither that is used for typical CATV transmission.
The external modulation reflector looks can provide optimum performance for many optical communication systems, but cost is expensive, high optical coupling loss (about 5 to about 7 decibels usually dB) and usually need to use complicated technology with the analog signal linearityization.
Therefore, in affiliated field, need to have improved optical transmission system and the assembly that improved systematic function, improved system reliability and/or acceptable systematic function are provided with the cost that reduces.
Summary of the invention
The present invention relates to a kind of simulating emitter, it does not need or has significantly reduced requirement to the predistortion circuit that usually is used for revising second order and third order distortion in the prior art.In addition, herein some embodiment of described simulating emitter by using direct modulation outside cavity gas laser and reduce cost and/or provide the level of warbling at application-specific.In addition, described herein simulating emitter has improved the inhibition level to SBS, thereby does not need the electronics dither or reduced the level of the required dither of this kind.Described herein progress reduced material and human cost, strengthened the link design performance, improved and made nargin and relaxed requirement to required technology specialty level in system makes.
The invention further relates to and comprise the alternative reflector that utilizes outside cavity gas laser (ECL or ECL laser), wherein strengthen and utilized the concrete property of ECL, especially so-called " one-sided butterfly " or " distortion bust " are significantly to improve second order and third order distortion, to provide warbling at application-specific simultaneously.The present invention has improved the technical merit of used simulating emitter in transmission radio frequency and light access etc. are used such as catv network, subcarrier multiplex system, on optical fiber.Simulating emitter that is comprised in the reflector of this kind described in the present invention and simulation ECL can be applicable to the operation wavelength band (and other wavelength bands-Ruo needs) of 1550nm or 1310nm.A schematic diagram that shows the exemplary embodiments of simulating emitter of the present invention among Fig. 1.
Simulating emitter of the present invention further relates to by the reflector that correctly designs ECL and comprise ECL and strengthens and use the distortion bust.Comprise (will further set forth in more detail hereinafter) in the main aspect of the present invention: the width that (i) increases the distortion bust is to relax requirement and the wideer margin of operation of realization to temperature control loop, to make temperature control loop commonly used be enough to simultaneously described reflector is locked in described distortion bust place in many cases and emission wavelength is locked in a setting; (ii) make described distortion bust move to a more stable ECL working region or form another away from described moding zone distortion bust away from the moding zone of described laser; (iii) with described warble to be adjusted to provide a favourable level of warbling at distortion bust place, wherein said warbling even as big as reducing or suppressing SBS but can not arrive the scope (in other words, warbling at application-specific) of restriction institute transmission signals greatly; And (iv) making up the self adaptation feedback control loop, the operation with described laser when can not be fully the operation of described laser being remained on described distortion bust place with advantageously little at second-order distortion and described temperature control loop is locked in distortion bust place.
These advantages belong to the row according to the advantage that various embodiments of the invention obtained that is hereinafter elaborated.
Description of drawings
Graphic and not drawn on scale herein and each assembly that is illustrated one graphic in and each relative size between graphic and ratio just schematically but not draw in proportion.
For ease of understanding, use identical reference numerals to represent each graphic common similar elements in possible place.
By graphicly considering hereinafter to describe in detail in conjunction with following, can more easily understand technology of the present invention, graphic in:
Fig. 1 a and 1b are the schematic block diagrams according to the typical simulation ECL reflector of certain embodiments of the invention, and described simulation ECL reflector comprises the simulation ECL laser of its low distortion bust and the high region alignment of warbling.
Fig. 2 is the schematic diagram of an ECL, and described ECL is based on (a) Fiber Bragg Grating FBG and (b) grating in the waveguide that writes on the planar lightwave circuit (PLC).
Fig. 3 describes the curve chart that typical second-order distortion (for example IMD2) changes with regulation pull-out, described typical second-order distortion is to be produced by a reflector that comprises a direct modulation system laser, and wherein the output of the optics of this laser is passed one and had the narrow bandwidth filter that out of phase postpones between response and the intensity modulated warbling.The dashed region of Fig. 3 forbids using based on the simulating emitter of ECL, and entire curve figure is applicable to the simulating emitter that optics strengthens simultaneously.
Fig. 4 describes a typical light and strengthens lasing light emitter, wherein can use the optics predistortion to improve the distortion performance of single Distributed Feedback Laser.
Fig. 5 describes second-order distortion with a curve chart that changes based on the working temperature of the reflector of ECL, it shows that one has the intermodulation distortion zone of one-sided butterfly curve (distortion bust), and this intermodulation distortion region list reveals the cycle behavior that the working temperature (for example it can be controlled by one thermoelectric (al) cooler-TEC) with ECL changes.
Fig. 6 one is depicted in a wherein one-sided butterfly curve (distortion bust) and a height and warbles in the specific embodiment of FBG design of simulation ECL of region alignment second-order distortion (for example IMD2) and the curve chart of warbling and changing with the temperature range between the moding.Describe experimental result.
Fig. 7 one is depicted in the curve chart that second-order distortion (for example IMD2) changed with laser temperature when Fiber Bragg Grating FBG (FBG) used (■) and do not use (▲) heat (heating) stress.As can be seen, thermal stress causes the distortion bust to be widened.
Fig. 8 is the curve chart of optical curve of describing the embodiment of a chirp grating.
Fig. 9 describes the curve chart that the FBG reflectance curve changes with the wavelength span.Should " knee " curve of spectrum be convenient to make OSBDP (distortion bust) and the height described in Figure 12 region alignment of warbling.
Figure 10 (upper, solid, curve) describes the curve chart that ECL wavelength (is unit with nm) changes with ECL working temperature (thermoelectric (al) cooler-TEC-temperature), its show when from heat to moding and hysteresis effect colder and when being chilled to that two kinds of situations of heat scan temperature.The lower dotted line curve is described second-order distortion (for example IMD2) and is changed with the ECL temperature and show distortion in the moding location.
Figure 11 one is depicted in the curve chart that IMD2 (lefthand vertical axis) and warble (righthand vertical axis) change with the temperature range between the moding in the situation that FBG has " knee curve ".As can be seen, with a wideer operating temperature range one second distortion bust appears.
The curve chart that Figure 12 changes with the temperature range between the moding for second-order distortion (for example IMD2) (lefthand vertical axis) and warble (righthand vertical axis) among the embodiment of the FBG design (FBG with knee curve) of a simulation ECL in a wherein one-sided butterfly curve (distortion bust) is warbled the example that aligns with maximum.This graphic simulation result of describing.
Figure 13 one is used at a simulation ECL reflector control OSBDP and makes itself and the schematic block diagrams in the adaptive control loop of the high region alignment of warbling.PLL represents phase-locked loop.
Figure 14 is a schematic block diagrams of describing an embodiment of a distortion locked laser (DLL).This simulating emitter assembly comprises the ECL who is locked by distortion that is locked in distortion bust place work of laser wherein.
Embodiment
After considering hereinafter explanation, the person of ordinary skill in the field will clearly realize that, teaching content of the present invention can be used at an easy rate design, make and/or use the simulated optical reflector that comprises assembly and subsystem thereof.
The present invention relates to comprise the optical analog reflector of outside cavity gas laser ECL and in broadcasting and Narrowcasting are used and be used to broadcast and purposes that Narrowcasting is used.Typical ECL structure provides in Fig. 2, and it comprises that one scribbles the laser diode 200 of an antireflective (AR) film or coating 201 on a side.Laser diode scribble a high reflection (HR) film or coating 202 with the opposed side of AR film, a reflection end of optical feedback cavity is provided thus.Except that laser diode 200, typical ECL comprises that also other are through selecting the optical element to work with laser diode combinedly.These optical elements and optical characteristics thereof can be represented by an optics transmitting function F easily.Optics transmitting function F () is generally a grating, is called a Bragg grating 203 sometimes.Bragg grating reflection and transmission are incided the different piece of the light on it from laser diode, are wherein reflected and the ratio of transmission especially depends on light wavelength.Therefore, in brief, Bragg grating plays speculum and filter.The reflection characteristic of Bragg grating 203 cooperates the optics cavity that forms laser with HR coating 202.The light that Bragg grating is crossed in transmission is the output of laser 204.
Because work (Laser emission) wavelength is generally the sensitivity function of temperature, so the common practice is to provide temperature sensing and temperature control device to keep a suitable precise dose and working temperature is remained in the desired temperature range, for example about 15 ℃-30 ℃ in ECL module or encapsulation.A kind of widely used temperature control device is thermoelectric (thermal electric or thermoelectric) cooler (TEC).
Can in the different embodiment that include, but is not limited to Fiber Bragg Grating FBG (FBG) or planar lightwave circuit (PLC) type ECL, make up ECL.Generally include usually by using UV commonly used to write technology based on the outside cavity gas laser of FBG shown in Fig. 2 (a) and be written to FBG 203 on the silica monomode fiber 205.In typical outside cavity gas laser, grating is write in the slab guide 206 based on silica as shown in Fig. 2 (b) based on PLC.In other ECL embodiment, can be with body grating as the optics transmitting function.Some embodiment comprise a tunable formula grating again, wherein can use such as come tuning optics propagation function with inferior technology: make grating spatial movement (for example using MEMS (micro electro mechanical system)) (MEMS) or use a RF signal and come tuning one based on sound-optical optical delivery function, or come the tunable formula filter of a tuning based thin film and additive method by application of heat or thermal stress.
One free-revving engine of optical information transmission is that increase information can be transmitted and the recipient that still can make this information uses or acceptable form receives the distance of this information with a kind of.This so-called " scope ".Extended effort has run into several challenges from optical delivery physics and engineering aspect.One of these challenges are to be present in warbling in the laser, and it interacts with chromatic dispersion in the optical fiber, thereby make seriously deterioration of the Signal Degrade that transmitted-usually.Another challenge is " stimulated Brillouin scattering " (SBS) phenomenon, and wherein the diaphragm of optical fiber or phonon and the light that transmitted interact and except that causing power also to cause the increase of noise and level of distortion saturated.SBS severally occurs and reduces one of nonlinear optical effect of systematic function.
Intermodulation distortion (IMD) is to reach one of the influence that will consider at the design optical transmission system when selecting or develop the assembly that is used for this kind system.IMD is characterised in that the influence on rank, the various mutual left and right sides, wherein second order IMD (IMD2 or compound second order-CSO) normally the most horrible in actual optical delivery.Reduce second-order distortion and be generally a kind of preferable program that is used for reducing the distortion of optical delivery and therefore increases scope.
For the information of carrying, modulate the light-i.e. directly modulation of being sent by the electric current of modulation drive laser usually by the diode 200 of launching laser.Yet, in typical laser diode, change drive current and can make the power output of laser and frequency the two all changes.Laser frequency is known as " warbling " and can be when the every variation of drive current 1 milliampere (mA) in the scope from several megahertzes (MHz) to about 1 gigahertz (GHZ) (GHz) with this variation of drive current.
Optical transmitting set is the preferable stable output wavelength that provides usually, and this expression is expected to warble lower (or being zero).Yet for the low reflector of warbling, SBS increases usually.In other words, when from a low reflector of warbling when an optical fiber is launched single wavelength, the SBS effect can produce unacceptable distortion noise and loss in the luminous power of being transmitted.Though different optical fiber can produce SBS more or less, typical optical transmission system is restricted to and uses existing, mounted fiber path.Therefore, the various solutions of SBS loss are focused on characteristic when light is being injected in the optical fiber usually.A kind of method is the laser diode that certain wavelength stability of sacrifice and support have the level of suitably warbling.In fact, changing emission wavelength by electronics " dither " (applying the drive current with fluctuation of having a mind to) wittingly is a kind of common method that is used to suppress, minimize or reduce SBS.An object of the present invention is to provide and a kind ofly not only had low distortion but also had the ECL reflector that is fit to the level of warbling used with common optical fiber, thereby reduce the loss that causes by SBS.As described herein, the ECL according to certain embodiments of the invention can realize this purpose with the cost that reduces than the prior art in the affiliated field.
Describe an interesting and useful ECL characteristic among Fig. 5, wherein a second-order distortion based on the simulating emitter of ECL is depicted as the function of ECL operating temperature (it is usually by TEC control).Second-order distortion occurs obviously reducing at some operating temperature place and can reappear at different operating temperature places as shown in FIG. 5 as can be seen.These " distortion busts " be usually expressed as shown in Figure 5 " one-sided butterfly distortion curve " (OSBDP).Produce in every way, control and row that to utilize these distortion busts are purposes of the present invention.
Fig. 3 shows by a second order intermodulation distortion IMD2 that system produced by direct modulation system laser constitution, a narrow bandwidth filter is passed in the output of the light of this direct modulation system laser, two different phase delay φ between wherein describe to warble response and the intensity modulated and wherein use two little amplitude sine tone that are positioned at frequency f 1 and f2 place to modulate this laser.One this type systematic can be by " optics a strengthens " laser constitution that wherein power output of a distributed Feedback (DFB) laser is coupled in the outside as shown in Figure 4 filter.Other system comprises described ECL herein.
Directly there is important difference in intermodulation distortion at optics laser enhanced device with the intermodulation distortion that comprises the simulating emitter of ECL.The one typical simulation reflector that comprises ECL shows an only one-sided butterfly curve in the distortion response diagram, this is by right-hand side shown in Figure 3 half (the shadow-free line) region representation; One simulating emitter that comprises optics laser enhanced device then has the intermodulation distortion zone in these two zones in the coverage diagram 3.
Comprise ECL as the simulating emitter of lasing light emitter have usually in the gamut that can come across the ECL operating temperature " one-sided butterfly distortion curve " (OSBDP).This type of one-sided butterfly distortion curve has several notable features, comprise level of distortion extremely low-be called " distortion bust " (to be usually less than pact-65dBc to approximately-70dBc) but come across usually less than in about 1 ℃ narrow relatively ECL temperature range.We notice that given temperature is generally the temperature that is set by the thermoelectric (al) cooler (TEC) that generally is integrated in the ECL assembly herein.This kind temperature does not need to be the operating temperature of whole ECL just, still, is the problem of our major concern because characteristic varies with temperature, so do not need absolute temperature measuring usually.
The experimental data demonstration one of being drawn among Fig. 5 is based on the only one-sided butterfly curve and the periodic property of this distortion bust in the whole service temperature range of ECL of the simulating emitter of ECL.
One aspect of the present invention relates to the width that ECL is designed to increase " one-sided butterfly " pattern or distortion bust.This can widen makes the ECL can be with the temperature range of the distortion value work that reduces.Clearly illustrate that as the experimental data among Fig. 5 and Fig. 6 the distortion bust of ECL is located usually less than about 1 ℃ at " mouth " of distortion bust, and only be 1 ℃ a few tenths of at the bottom periphery of distortion bust.There are the various methods that are used to increase distortion bust width, include, but is not limited to:
(i) on as the grating of the optical delivery function of ECL (grating in for example FBG, or the PLC waveguide, or body grating, or by the formed grating of sound-optical effect, and other gratings), apply a stress.Can come stress application by machinery or thermal effect or the combination of the two.Show an example among Fig. 7, wherein when thermal stress being applied to the FBG of a simulation ECL, obtain the distortion bust and add broad effect.
(ii) adopt novel grating design, so that described optical curve produces wideer distortion bust.These grating designs comprise non-chirp grating, and it has a half-peak overall with and is in about 100pm to about 400pm (pm=micromicron=10
-12Rice) the gaussian-shape optical curve in the scope.The design of these gratings also comprises the chirp grating shown in Fig. 8, and has one and make the grating reflection rate curve have as shown in Figure 9 the FBG of the structure of " knee " shape.
Outside cavity gas laser shows the working region that is known as the moding zone usually, and in the moding zone, it is metastable fixed that the output of laser becomes, thereby causes the characteristics of luminescence abrupt change of laser.Therefore, the preferable optical transmitting set that makes is away from the moding regional work.
Another aspect of the present invention relates to be made, and " one-sided butterfly " pattern or distortion bust move to a more stable ECL working region away from the moding zone.As describing among Figure 10, the distortion bust among the simulation ECL comes across wherein laser wavelength in some temperature interval near the moding of " jump " suddenly usually.Owing to have hysteresis effect in the moding location, so the position of a kind of wherein distortion of preferred configuration bust is away from the simulation ECL of moding or form another distortion bust away from the moding zone.A kind of method that is used to make the distortion bust to move or form away from the second distortion bust in a moding zone away from a moding is by the design of grating and/or by applying controlled stress to grating.In the time of in a FBG with the curve of " knee " shown in Figure 9 being incorporated into a simulation ECL, the second distortion bust among Figure 11 is enhanced.The additive method that is used to handle the distortion bust comprises and adopts a design to have to have big relatively FWHM the FBG of the gaussian-shape optical curve of (usually between from about 200pm extremely in the scope of about 400pm).
Another aspect of the present invention relates to being customized to warbling provides a favourable level of warbling at distortion bust place, wherein said warbling is high enough to fully reduce SBS but is unlikely to big maximum magnitude to restriction institute transmission of analogue signal.SBS is generally to limiting the limiting factor of transmission link performance because the nonlinear effect in low warble character and the optical fiber of ECL interacts, thereby has a simulating emitter that comprises utmost point low distortion level (for example appearing at the minimum value place of distortion bust or near level of distortion) ECL and can't automatically guarantee enough signal performances on the analog optical fiber link.In addition, the SBS inhibition method of existing use dither (it is at the exploitation of DFB and external modulation source) also may be not enough to suppress the SBS based in the reflector of ECL except that the cost height.
A kind of tackle because of the method with the challenge that brings based on the relevant SBS of the reflector of ECL be to increase the level of warbling, keep extremely low distortion simultaneously.This can be according to some embodiment of the present invention, by will (OSBDP) being arranged to and (or " align " along the higher zone of warbling) occurring and realize with the height identical operating temperature place, zone that warbles corresponding to " the one-sided butterfly distortion curve " of ECL distortion bust.This makes it possible to transmission low distortion signal on an analog optical fiber link, and can not cause Signal Compression or other ill-effects by SBS.Importantly should point out in conjunction with some embodiment of the present invention; even in the higher zone of warbling of this kind of ECL; the value of warbling that is produced by reflector described herein is compared also enough little with the DFB of standard, thereby can make the deterioration that is caused by optical fiber dispersion be avoided or drop to manageable degree usually.
Fig. 6 (experimental result) and Figure 12 (simulation result) show two kinds of different designs of an ECL simulating emitter, and wherein an one-sided butterfly curve (or distortion bust) is along the high region alignment of warbling.Low distortion (OSBDP or distortion bust) aligns with high this kind of warbling the zone and can realize at an arbitrary method or a combination by several methods.A kind of method relates to the curve of spectrum of revising exocoel.One embodiment of the modified exocoel curve of spectrum is what is called depicted in figure 9 " knee " the shape curve of spectrum.This curve among Fig. 9 makes the distortion bust can the relative high region alignment of warbling with.The additive method that is used for obtaining identical or similar effect comprises the curve of spectrum that uses chirped light spectral curve (write optical fiber producing the chirp grating of curve shown in Figure 8, or write the chirp grating in the waveguide of PLC) or wherein warble by outside approach (for example by gradient that heat or mechanical stress produced) introducing.Such as, also can by for example by people such as B.J.Eggleton " being used to have the dual optical fiber upper film heater (Dual on-fiber thin film heaters for fiber gratings with independently adjustablecentral wavelength and chirp) of the centre wavelength that can independently adjust and the fiber grating of warbling " (
Bragg Gratings, Photosensitivity, and Poling in Glass Waveguides 1999 Technical Digest, the 32nd page) described in the appropriate combination of cone-shaped metalization introduce heat and warble, the full content of this article is incorporated herein with way of reference for various purposes.
Another aspect of the present invention relates to design and makes up the self adaptation feedback control loop, so that the work of laser is locked on distortion bust wherein and the desired operating temperature at the region alignment of warbling of application-specific i.e. " distortion locking ".An example in this kind of graphic extension adaptive control loop among Figure 13.The use of the feedback control loop that is proposed is to have utilized the useful feature that is illustrated as the ECL of distortion bust hereinbefore, and comparable simulating emitter described in the prior art significantly improves fine ratio of product.
Because OSBDP appears in the narrow ECL temperature range of a distortion sensitivity very high (usually between from about 510dB/ ℃ to about 10dB/ ℃ scope) (usually less than about 1 ℃), so preferablely accurately adjust the skew that operating temperature is put the environmental condition that compensates variation and worn out and cause because of reflector.
Since the position of distortion minimum value basically with frequency-independent, therefore can make up feedback loop by applying two pilot tone signals of telecommunication that are near frequency f 1, f2 (wherein f2=f1+fo) that produce by same source.Preferable these frequencies are chosen to not disturb existing RF analog carrier in the CATV/QAM transmission bandwidth.
As the RF pilot signal f1 that has a fixed skew with two and f2 (it is produced by same oscillator usually) when being applied to the ECL reflector, then because the mechanism of the basic distortion that causes because of nonlinear optical effect, the light output of reflector will have a second order distortion signal that is in f=f2-f1 or f=f2+f1.Can be by using optical tapoff coupler as shown in fig. 1 or picking out this and export light signal by using from the ECL optical fiber head, to divide from the faceted light in the back of ECL laser.But in both cases, the photodetector that is used for transmitting photo-signal should have an enough big bandwidth, and correctly look-in frequency is the signal of f thus.As shown in Figure 13, described signal comes filtering by BP (band is logical) filter usually, extracting preceding amplification of phase information (homophase and quadrature component), uses a phase detector and a reference oscillator usually then.
The minimum value (bottom of distortion bust) that the operating temperature of ECL reflector can roughly be set in OSBDP is located or a little on the side of its right side (higher temperature).If with temperature set for make ECL minimum distortion (phase place=0) locate or near work, then the direction of error signal Δ S will depend on the variation of quadrature component symbol.If the temperature working point set for make its bias distortion minimum value, then the direction of error signal Δ S will depend on the relative variation of signal amplitude.In addition, because the left side gradient has different phase symbols with the right side inclination, therefore the symbol of phase signal can be prevented that as a control signal control loop is out of control.
Supposition now environmental change slowly under the condition operating point be offset δ T＞0 and arrived Top=To+ δ T, wherein To is initial ECL operating temperature (a TEC temperature).In order to compensate this kind variation, can produce an error signal.Because variation of temperature, the amplitude of distorted signal S (f2-f1) will increase and move apart departure S (To) usually.(fo To) and by a gain block of control loop is amplified will to produce error signal Δ S=S (fo, To+ δ T)-S.Then, by a voltage-to-current converter sensitivity is applied to the TEC control circuit with compensation δ T by the signal that formed of K.This kind self adaptation feedback loop comprises those skilled in the art institute modification easy to know and alternate embodiment, and simulation ECL reflector can be compensated at environmental change and because of the variation that causes of wearing out.
Another aspect of the present invention relates to a distortion locking-type ECL is integrated in the sub-assembly of a reflector (it is the subclass of a simulating emitter).We are called a distortion locking-type laser (DDL) with the sub-assembly of this reflector and it are shown among Figure 14.DLL is as a building block of simulating emitter.Sub-assembly of this reflector or DLL comprise an ECL, this ECL have enhancing the distortion bust and this distortion bust place or near have one and be applicable to that improving SBS suppresses and the level of warbling of not obvious sacrifice link range.Described transmitter sub-system also generally include be used for ECL be locked into distortion bust place or near the dynamical feedback control loop of operation, include, but is not limited to the embodiment of this kind control loop described herein.The drive electronics such as circuit that the sub-assembly of described reflector also comprises such as RF amplifier, temperature controller and is used for the DLL operating state is finely tuned.In addition, can optionally comprise predistortion circuit according to the simulating emitter of simulating ECL comprising of certain embodiments of the invention, it is used for revising the deterioration of second order and third harmonic distortion when light signal passes optical fiber in ECL.
In addition, can optionally comprise the circuit that electronic dispersion compensation is provided according to the simulating emitter of simulating ECL comprising of certain embodiments of the invention, this circuit is propagated the Signal Degrade that the chromatic dispersion that produces causes being used on the ECL to alleviate because of signal in standard single-mode fiber.
In addition, the ECL that is contained in the simulating emitter according to certain embodiments of the invention can optionally comprise a coaxial optical isolator, suppressing luminous power and to prevent that its coupling is back in the chamber of ECL, reduces thus or eliminates a main noise source in the aaaanalog transmission system.
Although show in detail in this article and each embodiment that comprises teaching content of the present invention has been described,, the person of ordinary skill in the field still comprises the different embodiment of these disclosure yet can easily dreaming up many other.
Claims (14)
1, a kind of temperature control outside cavity gas laser, it comprises:
One laser and one or more temperature controller, the operating temperature of wherein said laser make described laser in the temperature province of the distortion bust of described laser or near work.
2, outside cavity gas laser as claimed in claim 1, wherein said laser have an operating temperature zone, and described operating temperature zone roughly has predetermined warbling at the described temperature province place of described distortion bust.
3, outside cavity gas laser as claimed in claim 2, wherein said predetermined warbling at application-specific.
Being in the described temperature province of described distortion bust does not appear in 4, outside cavity gas laser as claimed in claim 1, the moding of wherein said laser.
5, outside cavity gas laser as claimed in claim 1, wherein said laser overlaps with at least one wavelength of the standard grid of wavelength division multiplexed systems substantially at the emission wavelength at the described temperature province place of described distortion bust.
6, outside cavity gas laser as claimed in claim 1, it comprises that further one or more temperature sensors and connect the feedback loop of described transducer and described temperature controller, so that the temperature of described laser remains in the described temperature province of described distortion bust substantially.
7, a kind of simulating emitter, it comprises a temperature control outside cavity gas laser as claimed in claim 1.
8, a kind of method of width that is used for to occur the temperature province of a distortion bust in a temperature control outside cavity gas laser control, described laser comprises that one is positioned at the light source of an optical feedback cavity, one end of wherein said optical feedback cavity is a part of reflective gratings, and described method comprises at least one operation in the following operation:
A) to described grating stress application, wherein said stress is thermal stress, mechanical stress or the two; And,
B) adopt a non-chirp grating as described partial reflection formula grating, described non-chirp grating has the transmission bandwidth in from about 100 micromicrons to the scope of about 400 micromicron fulls width at half maximum (FWHM); And,
C) adopt a chirp grating as described partial reflection formula grating; And,
D) adopt one to have the grating of a knee shape reflectance curve as described partial reflection formula grating.
9, a kind of method that a temperature control outside cavity gas laser is carried out the distortion locking, it comprises:
A) apply two radio frequency pilot signals to described outside cavity gas laser, in the described optics output of described laser, form a distorted signal that is in the described difference on the frequency of described pilot signal thus with different frequency and a fixed skew; And,
B) from described distorted signal, extract phase information; And,
C) produce an error signal by described phase information; And,
D) temperature of the described temperature control outside cavity gas laser of adjustment is to be reduced to described error signal one near zero value.
10, a kind of method that a temperature control outside cavity gas laser is carried out the distortion locking, it comprises:
Use a thermoelectric (al) cooler and a temperature sensor, described thermoelectric (al) cooler and described temperature sensor form a thermal control loop, the described operating temperature of the described exocoel of described outside cavity gas laser is remained on the value substantially, described output signal with described laser is locked in a distortion bust and a transmitted wave strong point simultaneously thus, and described emission wavelength is in a wavelength place of the standard grid of wavelength division multiplexed systems substantially.
11, a kind ofly be used to broadcast and the simulating emitter at application-specific of Narrowcasting transmission, described reflector is with the wavelength work at a wavelength place that is positioned at the standard grid of wavelength division multiplexed systems substantially, and described reflector comprises: one be locked into basic simultaneously at a distortion bust place and at the temperature control outside cavity gas laser of the predetermined place's work of warbling.
12, outside cavity gas laser as claimed in claim 1, it further comprises and acts on described laser to reduce the second harmonic distortion, third harmonic distortion or the predistortion circuit of the two.
13, outside cavity gas laser as claimed in claim 1, it further comprises the circuit that electronic dispersion compensation is provided, the described circuit function that electronic dispersion compensation is provided in described laser to alleviate the described optical signalling that is produced by described laser and in an optical fiber, propagate and the Signal Degrade that causes.
14, outside cavity gas laser as claimed in claim 1, it further comprises one coaxial (in-line) optical isolator, is coupled back in the described chamber of described laser with the luminous power that suppresses to be reflected.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11/097,746 US7548567B2 (en) | 2004-04-02 | 2005-04-01 | Analog transmitter using an external cavity laser (ECL) |
| US11/097,746 | 2005-04-01 |
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| Publication Number | Publication Date |
|---|---|
| CN101013923A true CN101013923A (en) | 2007-08-08 |
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| CN 200610066361 Pending CN101013923A (en) | 2005-04-01 | 2006-03-30 | Analog transmitter using an external cavity laser (ecl) |
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| CN (1) | CN101013923A (en) |
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| CN104486001A (en) * | 2014-12-02 | 2015-04-01 | 苏州市欧博锐自动化科技有限公司 | Optical transmitter based on second-order high-pass filter circuit |
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| JP2010011098A (en) * | 2008-06-27 | 2010-01-14 | Fujitsu Ltd | Optical transmission device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104486001A (en) * | 2014-12-02 | 2015-04-01 | 苏州市欧博锐自动化科技有限公司 | Optical transmitter based on second-order high-pass filter circuit |
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