CN2648708Y - Light isolator - Google Patents

Abstract

The utility model discloses an optical isolator that can work normally in a relatively wide range of temperature and wavelength. The utility model mainly comprises a fiber collimator (1), a polarized light spectroscopic device (3) with an oblique, a faraday rotator (4), a one fourth wave plate (5) that has an optical axis angle of 45 degrees with the polarized light spectroscopic device (3), a full-wave plate (6) that has an optical axis angle of 65 plus or minus 15 degrees with the polarized light spectroscopic device (3), a polarized light spectroscopic device (7) with an oblique, a polarized light spectroscopic device (8) with an oblique, a faraday rotator (9) that has a different rotation temperature characteristic with the faraday rotator (4), a one fourth wave plate (10) that has an optical axis angle of 45 degrees with the polarized light spectroscopic device (8), a full-wave plate (11) that has an optical axis angle of 65 plus or minus 15 degrees with the polarized light spectroscopic device (8), a polarized light spectroscopic device (12) with an oblique and a fiber collimator (13). The utility model can be used in the field of the fiber communication.

Description

A kind of optical isolator

Technical field

The utility model relates to a kind of optical isolator that is applied to optical-fibre communications field.

Background technology

In optical-fibre communications, optical isolator can be widely used in light source, optical transmission system etc. as important element in the passive device.Optical isolator commonly used at present, the second polarised light splitter spare that it comprises first optical fiber collimator and second optical fiber collimator and sets gradually the first polarised light splitter spare at band oblique angle therebetween, faraday rotator, quarter wave plate, full-wave plate, band oblique angle.The function that it is realized is to make the incident laser of first optical fiber collimator from the second optical fiber collimator outgoing, and promptly forward leads to light, and the incident laser of second optical fiber collimator can not be from first optical fiber collimator outgoing, the i.e. reverse isolation.But because faraday rotator is relevant with the temperature of polarization light wavelength and this device environment of living in to the angle of polarised light rotation, the optical isolator of prior art can only be realized above-mentioned function in the temperature and the wave-length coverage of relative narrower.

The utility model content

Technical problem to be solved in the utility model is to overcome the deficiencies in the prior art, and a kind of optical isolator is provided, and this optical isolator can be realized the logical light of forward, the function of reverse isolation in the temperature of a broad and wave-length coverage.

The technical scheme that the utility model adopted is: the utility model mainly by first optical fiber collimator, the band oblique angle the first polarised light splitter spare, the second polarised light splitter spare and second optical fiber collimator at first faraday rotator, first quarter wave plate, first full-wave plate, band oblique angle are formed, and also are provided with the 3rd polarised light splitter spare, second faraday rotator, second quarter wave plate, second full-wave plate and the 4th polarised light splitter spare at band oblique angle between described second polarised light splitter spare and described second optical fiber collimator successively; The optically-active temperature characterisitic of described second faraday rotator and described first faraday rotator is inequality; The optical axis included angle of the optical axis of described first quarter wave plate and the described first polarised light splitter spare is 45 degree, the optical axis included angle of the optical axis of described second quarter wave plate and described the 3rd polarised light splitter spare is 45 degree, the optical axis included angle of the optical axis of described first full-wave plate and the described first polarised light splitter spare is 65 ± 15 degree, and the optical axis included angle of the optical axis of described second full-wave plate and described the 3rd polarised light splitter spare is 65 ± 15 degree.

The described first polarised light splitter spare, the second polarised light splitter spare, the 3rd polarised light splitter spare, the 4th polarised light splitter spare are birefringece crystals, also can be PBS prism or wollaston prism.

The beneficial effects of the utility model are: because the utility model is provided with two faraday rotators that the optically-active temperature characterisitic is inequality, its temperature correlated characteristic compensates mutually, thereby the utility model can realize in a wider temperature range that forward leads to light, the function of reverse isolation; Because the utility model also is provided with and has axial two quarter wave plates of specific light and two full-wave plates, wherein the optical axis included angle of the optical axis of first quarter wave plate and the first polarised light splitter spare is 45 degree, the optical axis included angle of the optical axis of second quarter wave plate and the 3rd polarised light splitter spare is 45 degree, the optical axis included angle of the optical axis of first full-wave plate and the first polarised light splitter spare is 65 ± 15 degree, the optical axis included angle of the optical axis of second full-wave plate and the 3rd polarised light splitter spare is 65 ± 15 degree, can compensate the wavelength dependent characteristics of faraday rotator preferably, thus the utility model can be in the wave-length coverage of a broad operate as normal.

Description of drawings

Fig. 1 is the utility model embodiment 1 optical texture and light path schematic diagram;

Fig. 2 is the logical light light path front elevational schematic of the utility model embodiment 1 forward;

Fig. 3 is the utility model embodiment 1 reverse isolation light path front elevational schematic;

Fig. 4 is the utility model embodiment 1 assembly structure schematic diagram;

Fig. 5 is the isolation curve synoptic diagram of the isolator of prior art;

Fig. 6 is the isolation curve synoptic diagram of the utility model embodiment 1;

Embodiment

Embodiment 1:

As shown in Figure 1, by the polarised light splitter spare 3 at optical fiber collimator 1, band oblique angle, form successively by the polarised light splitter spare 7 at faraday rotator 4, quarter wave plate 5, full-wave plate 6, band oblique angle, polarised light splitter spare 8, faraday rotator 9, quarter wave plate 10, full-wave plate 11 and the polarized light splitting device 12 at band oblique angle and optical fiber collimator 13 for the utility model; Described polarised light splitter spare the 3,7,8, the 12nd, birefringece crystal.

Wherein, optical fiber collimator 1,13 main focusing, the alignment functions of realizing laser, it is made up of optical fiber head and condenser lens, and described condenser lens is a GRIN Lens, can certainly be spherical lens.

Polarised light splitter spare 3,7,8,12 all has certain oblique angle.When laser is imported by optical fiber collimator 1, when being forward entrance, the function of polarised light splitter spare 3,8 is that the laser with incident resolves into the vertical two-beam in polarization direction---ordinary light and extraordinary ray, and make it have certain included angle, and and the function of polarised light splitter spare 7,12 is two-beams that the polarization direction with certain included angle of incident is vertical---ordinary light and extraordinary ray synthesize the two-beam of the parallel basic coincidence of direction; When laser is imported by optical fiber collimator 13, when being reverse incident, the function of polarised light splitter spare 7,12 is that the laser with incident resolves into the vertical two-beam in polarization direction---ordinary light and extraordinary ray, and make it have certain included angle, and the function of polarised light splitter spare 3,8 is two-beams that the polarization direction with certain included angle of incident is vertical---ordinary light and extraordinary ray refraction the becoming bigger two-beam of angle.

The optical axis direction of polarised light splitter spare 3 is any, and in order to design and produce conveniently, present embodiment is set on the logical light face that becomes 22.5 degree with horizontal line, can certainly be on the logical light face that becomes 22.5 degree with vertical curve; The optical axis of the optical axis of polarised light splitter spare 7 and polarised light splitter spare 3 is in parallel plane, and in angle of 45 degrees, its direction is determined by faraday rotator 4 direction of rotation; The optical axis direction of polarised light splitter spare 8 also can be for arbitrarily, and for the compensating polarization mode dispersion parameter, present embodiment is set in the plane parallel with the optical axis of polarised light splitter spare 7, and direction is vertical; And the optical axis direction of the optical axis direction of polarised light splitter spare 12 and polarised light splitter spare 8 is in same parallel plane, and angle becomes 45 degree, and the angle direction is determined by faraday rotator 9 direction of rotation.

Described faraday rotator 4,9 adopts the different faraday rotators of optically-active temperature characterisitic, and the wavelength of its rotation 45 degree is inconsistent.Isolation value when like this, the isolation value in the time of just can making the high temperature long wave is with the low temperature shortwave equates that these two parameters are extreme values of isolation in whole temperature and the wavelength band.Described quarter wave plate 5,10 and full-wave plate the 6, the 11st are provided with in order to compensate the inconsistent of faraday rotator 4,9 optically-active angles under different wave length and the different temperatures situation, and wherein, described full- wave plate 6,11 can be substituted by half-wave plate; The optical axis included angle of the optical axis of described quarter wave plate 5 and described polarised light splitter spare 3 is 45 degree, and the optical axis included angle of the optical axis of described quarter wave plate 10 and described polarised light splitter spare 8 is 45 degree

The principle of present embodiment is as described below:

As shown in Figure 2, behind the laser focusing collimation of the optical fiber of optical fiber collimator 1 input, it is mutually vertical and the polarised light of certain angle arranged to be divided into the two-way direction of vibration by polarised light splitter spare 3, pass faraday rotator 4 afterwards, polarization direction rotation 45 degree of two-beam, again by quarter wave plate 5 and full-wave plate 6, produce certain phase delay, behind polarised light splitter spare 7, two parallel bundle directional lights of direction when two bundles have the polarised light of angle to become with incident polarized light light-splitting device 3, enter polarised light splitter spare 8 then, two bundle directional lights are reflected the two bundle polarised lights that become to have certain angle, pass faraday rotator 9 again, the two-beam polarization direction rotates 45 degree once more, produce certain phase delay by quarter wave plate 10 and full-wave plate 11 again, the parallel a branch of directional light of direction when making two bundles have the polarised light of angle to synthesize with its incident polarized light light-splitting device 8 by polarised light splitter spare 12, the condenser lens by optical fiber collimator 13 is coupled to its optical fiber output at last.

As shown in Figure 3, when the laser of the optical fiber of optical fiber collimator 13 input arrives polarised light splitter spare 12, laser is divided into the vertical and polarised light that have certain angle in two bundle polarization directions, behind full-wave plate 11 and quarter wave plate 10, produces certain phase delay.

Optical axis direction is that the Jones matrix expression of the full-wave plate of α is

$\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="Y0326809300101.png,Y0326809300111.png"\; state="\{\{state\}\}">M</figure-callout>}1=\left[\begin{array}{cc}\cos \left(\mathrm{\&alpha;}\right)& \sin \left(\mathrm{\&alpha;}\right)\\ -\sin \left(\mathrm{\&alpha;}\right)& \cos \left(\mathrm{\&alpha;}\right)\end{array}\right]\&CenterDot;\left[\begin{array}{cc}\exp (\mathrm{li}\&CenterDot;\mathrm{\&delta;}1)& 0\\ 0& 1\end{array}\right]\&CenterDot;\left[\begin{array}{cc}\cos \left(\mathrm{\&alpha;}\right)& -\sin \left(\mathrm{\&alpha;}\right)\\ \sin \left(\mathrm{\&alpha;}\right)& \cos \left(\mathrm{\&alpha;}\right)\end{array}\right]$

Optical axis direction is that the Jones matrix expression of the quarter wave plate of β is

$M2=\left[\begin{array}{cc}\cos \left(\mathrm{\&beta;}\right)& \sin \left(\mathrm{\&beta;}\right)\\ -\sin \left(\mathrm{\&beta;}\right)& \cos \left(\mathrm{\&beta;}\right)\end{array}\right]\&CenterDot;\left[\begin{array}{cc}\exp (\mathrm{li}\&CenterDot;\mathrm{\&delta;}2)& 0\\ 0& 1\end{array}\right]\&CenterDot;\left[\begin{array}{cc}\cos \left(\mathrm{\&beta;}\right)& -\sin \left(\mathrm{\&beta;}\right)\\ \sin \left(\mathrm{\&beta;}\right)& \cos \left(\mathrm{\&beta;}\right)\end{array}\right];$

Two bundle polarised lights pass through faraday rotator 9 again, polarization direction rotation θ degree, θ=45+K0* (λ-λ c)+K1* (T-T0), K0 is the angle dispersion coefficient of faraday rotator, λ is an incident light wavelength in a vacuum, and λ c is the wavelength points of optical rotation plate rotation 45 when spending, and K1 is the temperature coefficient of faraday rotator, T0 is the temperature value of optical rotation plate rotation 45 when spending, and its matrix notation formula is

$M3=\left[\begin{array}{cc}\cos \left(\mathrm{\&theta;}\right)& -\sin \left(\mathrm{\&theta;}\right)\\ \sin \left(\mathrm{\&theta;}\right)& \cos \left(\mathrm{\&theta;}\right)\end{array}\right]$

Because faraday rotator is irrelevant to the transmission direction of polarised light direction of rotation and light, so, when this two bundles polarised light enters polarised light splitter spare 8, originally be that the polarised light of ordinary light is extraordinary ray in polarised light splitter spare 8 with respect to polarised light splitter spare 12, originally be that the polarised light of extraordinary ray is ordinary light polarised light splitter spare 8 in respect to polarised light splitter spare 12, so two emergent light angles further increase; In like manner, this two bundles polarised light passes through polarised light splitter spare 7, full-wave plate 6, quarter wave plate 5, faraday rotator 4, polarised light splitter spare 3 more successively, wherein faraday rotator 4 has certain amount of deflection with respect to the λ c parameter of faraday rotator 9, if be λ c1, this numerical value depends on the wave-length coverage and the temperature range of isolator work, angle by back two bundle polarised lights further increases, therefore, faraday rotator 4 optically-active angles are θ 1=45+K0* (λ-λ c1)+K1* (T-T0), and its matrix is

$\mathrm{<figure-callout\; id="4"\; label="M"\; filenames="Y0326809300111.png,Y0326809300121.png"\; state="\{\{state\}\}">M</figure-callout>}4=\left[\begin{array}{cc}\cos \left(\mathrm{\&theta;}1\right)& -\sin \left(\mathrm{\&theta;}1\right)\\ \sin \left(\mathrm{\&theta;}1\right)& \cos \left(\mathrm{\&theta;}1\right)\end{array}\right]$

Therefore, the Jones matrix during reverse isolation is:

$\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right]\&CenterDot;\mathrm{<figure-callout\; id="4"\; label="M"\; filenames="Y0326809300111.png,Y0326809300121.png"\; state="\{\{state\}\}">M</figure-callout>}4\&CenterDot;M2\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="Y0326809300101.png,Y0326809300111.png"\; state="\{\{state\}\}">M</figure-callout>}1\&CenterDot;\left[\begin{array}{cc}0.5& 0.5\\ 0.5& 0.5\end{array}\right]\&CenterDot;\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right]\&CenterDot;\mathrm{<figure-callout\; id="3"\; label="M"\; filenames="Y0326809300111.png,Y0326809300121.png"\; state="\{\{state\}\}">M</figure-callout>}3\&CenterDot;M2\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="Y0326809300101.png,Y0326809300111.png"\; state="\{\{state\}\}">M</figure-callout>}1\&CenterDot;\left[\begin{array}{cc}0.5& 0.5\\ 0.5& 0.5\end{array}\right]\&CenterDot;\left[\begin{array}{c}\frac{\sqrt{3}}{2}\\ \frac{1}{2}\end{array}\right]$ And

$\left[\begin{array}{cc}0& 0\\ 0& 1\end{array}\right]\&CenterDot;\mathrm{<figure-callout\; id="4"\; label="M"\; filenames="Y0326809300111.png,Y0326809300121.png"\; state="\{\{state\}\}">M</figure-callout>}4\&CenterDot;M2\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="Y0326809300101.png,Y0326809300111.png"\; state="\{\{state\}\}">M</figure-callout>}1\&CenterDot;\left[\begin{array}{cc}0.5& -0.5\\ -0.5& 0.5\end{array}\right]\&CenterDot;\left[\begin{array}{cc}0& 0\\ 0& 1\end{array}\right]\&CenterDot;\mathrm{<figure-callout\; id="3"\; label="M"\; filenames="Y0326809300111.png,Y0326809300121.png"\; state="\{\{state\}\}">M</figure-callout>}3\&CenterDot;M2\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="Y0326809300101.png,Y0326809300111.png"\; state="\{\{state\}\}">M</figure-callout>}1\&CenterDot;\left[\begin{array}{cc}0.5& -0.5\\ -0.5& 0.5\end{array}\right]\&CenterDot;\left[\begin{array}{c}\frac{\sqrt{3}}{2}\\ \frac{1}{2}\end{array}\right]$

Light intensity when the faraday rotator 4,9 of full- wave plate 6,11 by selecting suitable optical axis angle and different centre wavelengths just can make oppositely by the utility model thus is all very little in very wide wave-length coverage and temperature range, can both guarantee in very wide wavelength, temperature range promptly that also device has very high isolation parameter value.In the present embodiment, the optical axis angle that full-wave plate 6 adopts and the optical axis included angle of polarised light splitter spare 3 are 60 degree, the optical axis angle that full-wave plate 11 adopts and the optical axis included angle of polarised light splitter spare 8 are 60 degree, the angle dispersion COEFFICIENT K 0 of faraday rotator 4,9 is 0.6, temperature coefficient K1 difference 0.7, temperature value T0 when rotation 45 is spent is 25 degrees centigrade, and the λ c1 of faraday rotator 4 is 1550nm, and the λ c1 of faraday rotator 9 is 1590nm.

Curve a, b among Fig. 5 is respectively the isolation curve synoptic diagram that the optical isolator of prior art when 70 degrees centigrade and 23 degrees centigrade is obtained in 1500～1690nm wave-length coverage, and curve c, d are respectively the isolation curve synoptic diagrams that the isolator of the prior art of band collocation structure when 70 degrees centigrade and 23 degrees centigrade is obtained in 1500～1690nm wave-length coverage.Can find out that from this figure the isolation curve flatness of the optical isolator of prior art is relatively poor, and little at band edge place isolation numerical value, with the variation of temperature sensitivity; And the optical isolator isolation numerical value at normal temperatures of prior art with collocation structure is bigger, but under the situation of temperature change, isolation numerical value produces bigger variation, show that its isolation value varies with temperature sensitivity, and this specific character is the requirement that is not suitable for communication system.

Curve A among Fig. 6, B, C are respectively the isolation curve synoptic diagrams that present embodiment is obtained in 1500～1690nm wave-length coverage in the time of-5,75,25 degrees centigrade.As can be seen from Figure, in each temperature range in whole wavelength band, the isolation parameter of present embodiment can satisfy the requirement of communication system all greater than 45dB.

Fig. 4 is the assembly structure schematic diagram of present embodiment: optical element is installed in the shell, and fixedlys connected with shell according to certain position relation, and the optical fiber tail end of optical fiber collimator 1,13 stretches out outside the shell.

Embodiment 2:

Polarised light splitter spare the 3,7,8, the 12nd of the present utility model, wollaston prism can certainly substitute with suitable substance P BS prism.

All the other are identical with embodiment 1.

Claims (2)

1, a kind of optical isolator, it mainly by optical fiber collimator (1), the band oblique angle polarised light splitter spare (3), the polarised light splitter spare (7) and the optical fiber collimator (13) at faraday rotator (4), quarter wave plate (5), full-wave plate (6), band oblique angle are formed, it is characterized in that, also be provided with polarised light splitter spare (8), faraday rotator (9), quarter wave plate (10), full-wave plate (11) and the polarised light splitter spare (12) at band oblique angle between described polarised light splitter spare (7) and the described optical fiber collimator (13) successively; Described faraday rotator (9) is inequality with the optically-active temperature characterisitic of described faraday rotator (4); The optical axis included angle of the optical axis of described quarter wave plate (5) and described polarised light splitter spare (3) is 45 degree, the optical axis included angle of the optical axis of described quarter wave plate (10) and described polarised light splitter spare (8) is 45 degree, the optical axis included angle of the optical axis of described full-wave plate (6) and described polarised light splitter spare (3) is 65 ± 15 degree, and the optical axis included angle of the optical axis of described full-wave plate (11) and described polarised light splitter spare (8) is 65 ± 15 degree.

2, a kind of optical isolator according to claim 1 is characterized in that, described polarised light splitter spare (3,7,8,12) is birefringece crystal or PBS prism or wollaston prism.

Images