CN101644794B - Monitoring method of optical coupler splitting ratio - Google Patents

Abstract

The present invention discloses a monitoring method of optical coupler splitting ratio, belonging to the technical field of optical communication. The method comprises the following steps: 1) connecting two ports (2) and (3) of an optical coupler at the same side; 2) inputting optical signals from one port (1) of the other side of the optical coupler; simultaneously, receiving the output optical signal power I4 at the other port (4) of the side, or receiving the output optical signal power I1 at the port (1); 3) adjusting the optical coupler so that the I4 is zero to obtain the coupler with equal splitting ratio, or confirming the optical coupler splitting ratio according to the received optical signal powers I1 and I4. Compared with the prior art, the invention realizes the precise control for coupler splitting, and can obtain the coupler with high precision and high reciprocity; simultaneously, the invention is not only suitable for the splitting ratio monitoring of normal single mode coupler and polarization-preserving coupler, but also has the characteristics of simple technology, low cost and good effect.

Description

A kind of monitoring method of optical coupler splitting ratio

Technical field:

The present invention relates to the splitting ratio method for supervising of the coupling mechanism of a kind of high precision, high reciprocity, belong to the optical communication technique field.

Background technology:

Photo-coupler is a kind of Passive Optical Components that is used for dividing by a certain percentage/closing light beam.In order to produce the photo-coupler of required splitting ratio, must in manufacturing process, strictness monitor splitting ratio.Be illustrated in figure 1 as the splitting ratio method for supervising schematic diagram that generally adopts at present: for the coupled system of 4 ports, it installs the PD detecting device additional by the light path at two ports of photo-coupler output, monitors after the beam split intensity of two paths of signals then respectively in real time and determines splitting ratio.The method that splitting ratio is monitored in known being used at present has transmission monitoring method (Japan special permission (disclosing) clear 63-175812), reflection monitoring method (Japan special permission (application) flat 1-275616).Most of manufacturing enterprise still monitors the intensity of two paths of signals after the beam split respectively and determines splitting ratio.Because the problems such as calibration between the detecting device, these methods all can not well accurately be controlled the splitting ratio of two ways of optical signals power after the beam split, especially in the high reciprocity of splitting ratio, just the power splitting ratio is under 50: 50 situations.

Summary of the invention:

The object of the present invention is to provide a kind of monitoring method of optical coupler splitting ratio, it is a kind ofly to utilize the phase shifts of coupling mechanism transposition arm 90 degree to be implemented in the photo-coupler manufacture process, the method that splitting ratio is monitored.This method is based on transposition arm and straight-through arm light signal coherent subtraction, and coherent signal is zero principle when amplitudes such as two paths of signals, thereby accurately controls power poor of two arms after the beam split by the difference of monitoring splitting ratio.

Technical method of the present invention is:

A kind of monitoring method of optical coupler splitting ratio, the transmission matrix of described photo-coupler is $\left[\begin{array}{c}{E}_2\\ {\mathrm{<figure-callout\; id="3"\; label="E"\; filenames="H2009100924155E00011.png,H2009100924155E00021.png"\; state="\{\{state\}\}">E</figure-callout>}}_3\end{array}\right]=\left[\begin{array}{cc}r& \mathrm{it}\\ \mathrm{it}& r\end{array}\right]\left[\begin{array}{c}{E}_1\\ {\mathrm{<figure-callout\; id="4"\; label="E"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">E</figure-callout>}}_4\end{array}\right],$ E wherein ₁, E ₂, E ₃, E ₄Be respectively the signal amplitude that inputs or outputs of four port coupler, t is a transposition arm amplitude coupling ratio, and r the steps include: for straight-through arm amplitude coupling ratio

1) connects two ports (2) and (3) that described photo-coupler is positioned at the same side;

2) from a port (1) input optical signal of described photo-coupler opposite side; Receive the optical signal power I of output simultaneously in the another port (4) of this side ₄, receive the optical signal power I that exports at described port (1) ₁

3) according to the optical signal power I that receives ₁And I ₄Determine this photo-coupler splitting ratio.

Further, according to formula I ₁=4r ²t ²a ²E _In ²And I ₄=a ²(r ²-t ²) ²E _In ²Determine described photo-coupler splitting ratio, wherein a is loss in the ring of formed ring in the described step 1), E _InBe the input optical signal amplitude.

Further, if described photo-coupler is a polarization-maintaining coupler, when then connecting photo-coupler and being positioned at two ports (2) of the same side and (3), the fast axle of port (2) and (3) be connected after slow axis is aimed at respectively.

Further, described input optical signal is a linearly polarized light, and the fast axle or the slow axis of the polarization direction of described linearly polarized light and described photo-coupler are consistent, and locates to receive respectively the output optical signal power of fast and slow axis in described port (1) and (4).

Further, if the linearly polarized light polarization direction of input is consistent with the slow axis of described photo-coupler, and fast of locating to receive respectively in port (1) and (4) exports optical signal power I _1yAnd I _4yNon-vanishing, then adjust coupling device and make I _1yAnd I _4yBe zero simultaneously, and then the slow axis output power I of detection port (1) and (4) _1xAnd I _4x

Further, described photo-coupler is a monomode coupler, and described input optical signal is circularly polarized light or linearly polarized light.

A kind of monitoring method of optical coupler splitting ratio, the transmission matrix of described photo-coupler is $\left[\begin{array}{c}{E}_2\\ {\mathrm{<figure-callout\; id="3"\; label="E"\; filenames="H2009100924155E00011.png,H2009100924155E00021.png"\; state="\{\{state\}\}">E</figure-callout>}}_3\end{array}\right]=\left[\begin{array}{cc}r& \mathrm{it}\\ \mathrm{it}& r\end{array}\right]\left[\begin{array}{c}{E}_1\\ {\mathrm{<figure-callout\; id="4"\; label="E"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">E</figure-callout>}}_4\end{array}\right],$ E wherein ₁, E ₂, E ₃, E ₄Be respectively the signal amplitude that inputs or outputs of four port coupler, t is a transposition arm amplitude coupling ratio, and r the steps include: for straight-through arm amplitude coupling ratio

1) connects two ports (2) and (3) that described photo-coupler is positioned at the same side;

2) from a port (1) input optical signal of described photo-coupler opposite side; Receive the optical signal power I of output simultaneously in the another port (4) of this side ₄

3) if the optical signal power I that receives ₄Be zero, then the transposition arm of this photo-coupler is identical with straight-through arm splitting ratio.

Further, if described photo-coupler is a polarization-maintaining coupler, when then connecting photo-coupler and being positioned at two ports (2) of the same side and (3), the fast axle of port (2) and (3) be connected after slow axis is aimed at respectively; Described input optical signal is a linearly polarized light, and the polarization direction of described linearly polarized light is consistent with the fast axle or the slow axis of described photo-coupler.

Further, if the optical signal power I that receives ₄Non-vanishing, and the linearly polarized light polarization direction of input is consistent with the photo-coupler slow axis, then detects the output power I of slow axis and fast axle respectively at port (4) _4xAnd I _4y, adjust coupling device earlier to fast shaft power I _4yBe zero, adjust coupling device again to slow axis output power I _4xBe zero.

Further, described photo-coupler is a monomode coupler, and described input optical signal is circularly polarized light or linearly polarized light.

The indication photo-coupler is one four port devices herein, as shown in Figure 2.Its transmission matrix can be expressed as:

$\left[\begin{array}{c}{E}_2\\ {\mathrm{<figure-callout\; id="3"\; label="E"\; filenames="H2009100924155E00011.png,H2009100924155E00021.png"\; state="\{\{state\}\}">E</figure-callout>}}_3\end{array}\right]=\left[\begin{array}{cc}r& \mathrm{it}\\ \mathrm{it}& r\end{array}\right]\left[\begin{array}{c}{E}_1\\ {\mathrm{<figure-callout\; id="4"\; label="E"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">E</figure-callout>}}_4\end{array}\right],$

Optical path analysis reference diagram of the present invention is at first considered single-mode fiber as shown in Figure 3, imports a monochromic beam E _InSimple case, note transposition arm amplitude coupling ratio is t, straight-through arm amplitude coupling ratio is r, loss is a in the ring, phase accumulation is φ.Incident light can be divided into two-way through coupling regime the time, the straight-through arm of leading up to arrives 2, E ₂=rE _In, E ₂Around one week of ring, be designated as at 3 places

E ' ₂Through leading directly to arm, be designated as E once more " in 4 port outgoing ₂=rE ' ₂Other one the tunnel, arrive 3 places through coupling regime by transposition arm in 1 port, be designated as E ₃=itE _In, arrive 2 places around ring after one week and be designated as

Be coupled to port 4 at 2 places by transposition arm, be designated as E " ₃=itE ' ₃This two-way finally goes out to interfere at 4 ports, forms output signal E _Out

Promptly carry out simple power detection at 4 ports, when the splitting ratio of transposition arm and straight-through arm was identical when power is zero, detection signal power was 0.If monitor at port one, then signal amplitude can be expressed as:

By top two formulas as can be known 1,4 port record power and be respectively I ₁And I ₄, itself and splitting ratio r, the t relation is as follows:

I ₁＝4r ²t ²a ²E _in ² (a)

I ₄＝a ²(r ²-t ²) ²E _in ² (b)

Can demarcate the splitting ratio of coupling mechanism more accurately by the power measurement of two ports.General, $\frac{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+I_4}{{\mathrm{<figure-callout\; id="4"\; label="I"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">I</figure-callout>}}_4}={\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2009100924155E00011.png,H2009100924155E00021.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+t^2}{r^2-t^2}\right)}^2,$ Work as r ²+ t ²=τ ²The time, the difference of power splitting ratio is $r^2-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2009100924155E00011.png,H2009100924155E00021.png"\; state="\{\{state\}\}">t</figure-callout>}}^2={\mathrm{\&tau;}}^2\sqrt{\frac{I_4}{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="H2009100924155E00011.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+I_4}}.$ Special, work as I ₄=0 o'clock power splitting ratio r ²=t ²

Further, if consider the polarization state of light signal, input signal can be expressed as E so _In=E _1x+ E _1y, promptly on two polarization directions of the slow axis of parallel and vertical polarization maintaining optical fibre, consider the behavior of signal respectively.Remember that still transposition arm amplitude coupling ratio is t, straight-through arm amplitude coupling ratio is r, and loss is a in the ring, and phase accumulation is φ.Consider that slow axis (x) is different with refractive index on fast axle (y) direction, coupling coefficient on the different polarization direction, loss and phase accumulation thereby difference, with subscript x, y is distinguished.With the slow axis is example, incident light E _1xCan be divided into two-way through coupling regime the time, the straight-through arm of leading up to arrives 2, E _2x=rE _1x, E _2xAround one week of ring, be designated as at 3 places E ' ₂Through leading directly to arm, be designated as E once more " in 4 port outgoing _2x=rE ' _2xOther one the tunnel, arrive 3 places through coupling regime by transposition arm in 1 port, θ has been changeed to slow axis in the polarization direction in coupling process, is designated as:

E _3x＝it _xE _1xcosθ

E _3y＝it _yE _1xsinθ

Signal on two polarization directions arrives 2 places around ring respectively after one week and is designated as:

At 2 places, the signal of two quadratures is coupled to port 4 by transposition arm respectively, is designated as:

E″ _3x＝it _xE′ _3xcosθ′-it _yE′ _3ysinθ′

E″ _3y＝it _xE′ _3xsinθ′+it _yE′ _3ycosθ′°

Twice signal through transposition arm and twice straight-through arm of process finally goes out to interfere at 4 ports.The input signal of final slow axis forms output signal E _4xAnd E _4y

In like manner, fast axis signal also can obtain the result of symmetry.

Under the situation of input signal polarization directions aligned slow-axis direction, aim at the fast and slow axis detection power of polarization maintaining optical fibre respectively.When fast shaft power that and if only if is zero, do not exist the polarization direction to rotate during the transposition arm coupling.At this moment, the power of slow axis deteriorates to

Similar with the output signal type of single-mode fiber, can use formula a, b estimation slow axis splitting ratio.Same when power when the splitting ratio of transposition arm and straight-through arm is identical when being zero, promptly ${r_x}^2=t_x^2,$ Detection signal power is 0.

Good effect of the present invention is:

The present invention realizes the principle of the difference of monitoring splitting ratio by utilizing the 90 degree phase shifts of coupling mechanism transposition arm, has realized the accurate control to the coupling mechanism beam split, can obtain the coupling mechanism of high precision, high reciprocity.The present invention not only is adapted to the monitoring of common monomode coupler and polarization-maintaining coupler splitting ratio, can be applied to simultaneously the monitoring that the polarization-maintaining coupler fast and slow axis is aimed at, and has that technology is simple, cost is low, good effectiveness.

Description of drawings

Fig. 1 is existing splitting ratio method for supervising schematic diagram;

Fig. 2 is a coupling mechanism block diagram of the present invention;

Fig. 3 is an optical path analysis reference diagram of the present invention;

Fig. 4 implements block diagram for the present invention monitors the coupling mechanism splitting ratio.

Embodiment

Now with embodiment the present invention is described in further details in conjunction with the accompanying drawings:

This detection method is applicable to follows all coupling mechanisms that above-mentioned transmission matrix is described.Monitoring coupling mechanism splitting ratio of the present invention is implemented block diagram as shown in Figure 4, and the inventive method implementation step is as follows:

If coupling mechanism is a single-mode system, then implementation step is as follows:

1.1 port loads input optical signal.Input light should be circularly polarized light.To such an extent as under the situation that the inner light path long enough of coupling mechanism linearly polarized light can not keep, the linearly polarized light input also can be used this method.

2. connect 2,3 ports.

3. in 4 port detection power, if 4 port detection power be 0 after the beam split two ways of optical signals power identical, r=t; If 4 port detection power are not 0, the received power that detects according to 1 port then, according to formula a, b can calculate the ratio of t and r.

If coupling mechanism is for protecting inclined to one side system, signal is propagated on slow axis, and then implementation step is as follows:

1.1 port loads input optical signal.Input optical signal should be linearly polarized light, and the slow axis x of aligning coupler.

2. connect 2,3 ports.Fast/the slow axis of 2,3 ports is aimed at during connection, and promptly fast axle is to fast axle, and slow axis is to slow axis.

3. in 4 port detection power.

A) the slow axis splitting ratio is 50: 50 if desired, i.e. r _x=t _x

I. if 4 port power I ₄Be 0, then before and after the coupling fast and slow axis direction all be held and beam split after two ways of optical signals power identical, r _x=t _x

Ii. if 4 port power I ₄Be not 0, then should detect output power respectively, promptly detect the output power of slow axis and fast axle respectively, I at 4 ports at fast axle and slow axis _4xAnd I _4yAdjust coupling device earlier to I _4yBe 0, then the fast and slow axis direction all is held before and after the expression coupling; Adjust coupling device again to I _4xBe 0, then two ways of optical signals power is identical after the beam split, r _x=t _x

B) splitting ratio of not reciprocity, i.e. r if desired _x≠ t _x, then elder generation detects the fast shaft power of 1 port and 4 ports, I respectively _1yAnd I _4yIf the two is not 0, then adjusting coupling device, to make the two be 0 simultaneously, and promptly the fast and slow axis direction all is held before and after the coupling.And then detect 1 port and 4 port slow axis power I _1xAnd I _4x, according to formula a, b can calculate the splitting ratio on the slow axis, r _x/ t _x, adjust coupled system to the power beam split ratio that needs.

In like manner, if coupling mechanism is the inclined to one side system of guarantor, this method can also be applied to signal and propagate on fast axle, perhaps two kinds of situations propagating on fast and slow axis simultaneously.

Claims (9)

1. monitoring method of optical coupler splitting ratio, the transmission matrix of described photo-coupler is

Wherein

E ₁, E ₂Be respectively the input signal amplitude of four port coupler, E ₃, E ₄Be respectively the output amplitude of four port coupler, t is a transposition arm amplitude coupling ratio, and r the steps include: for straight-through arm amplitude coupling ratio

1) connects second port (2) and the 3rd port (3) that described photo-coupler is positioned at the same side;

2) from one first port (1) input optical signal of described photo-coupler opposite side; Receive the optical signal power I of output simultaneously at one the 4th port (4) of this side ₄, receive the optical signal power I that exports at described first port (1) ₁

3) according to the optical signal power I that receives ₁And I ₄Determine this photo-coupler splitting ratio; I wherein ₁=4r ²t ²a ²E _In ²With

I ₄=a ²(r ²-t ²) ²E _In ², a is loss in the ring of formed ring in the described step 1), E _InBe the input optical signal amplitude.

2. the method for claim 1, it is characterized in that if described photo-coupler is a polarization-maintaining coupler, when then connecting photo-coupler and being positioned at second port (2) of the same side and the 3rd port (3), the fast axle of second port (2) and the 3rd port (3) be connected after slow axis is aimed at respectively.

3. method as claimed in claim 2, it is characterized in that described input optical signal is a linearly polarized light, the fast axle or the slow axis of the polarization direction of described linearly polarized light and described photo-coupler are consistent, and locate to receive respectively the output optical signal power of fast and slow axis at described first port (1) and the 4th port (4).

4. method as claimed in claim 3 is characterized in that if the linearly polarized light polarization direction of importing is consistent with the slow axis of described photo-coupler, and the fast axle output optical signal power I that locates to receive respectively at first port (1) and the 4th port (4) _1yAnd I _4yNon-vanishing, then adjust coupling device and make I _1yAnd I _4yBe zero simultaneously, and then detect the slow axis output power I of first port (1) and the 4th port (4) _1xAnd I _4x

5. the method for claim 1 is characterized in that described photo-coupler is a monomode coupler, and described input optical signal is circularly polarized light or linearly polarized light.

6. monitoring method of optical coupler splitting ratio, the transmission matrix of described photo-coupler is

Wherein

E ₁, E ₂Be respectively the input signal amplitude of four port coupler, E ₃, E ₄Be respectively the output amplitude of four port coupler, t is a transposition arm amplitude coupling ratio, and r the steps include: for straight-through arm amplitude coupling ratio

1) connects second port (2) and the 3rd port (3) that described photo-coupler is positioned at the same side;

2) from one first port (1) input optical signal of described photo-coupler opposite side; While is at one the 4th port of this side

(4) receive the optical signal power I that exports ₄

3) if the optical signal power I that receives ₄Be zero, then the transposition arm of this photo-coupler is identical with straight-through arm splitting ratio.

7. method as claimed in claim 6, it is characterized in that if described photo-coupler is a polarization-maintaining coupler, when then connecting photo-coupler and being positioned at second port (2) of the same side and the 3rd port (3), the fast axle of first port (2) and the 3rd port (3) be connected after slow axis is aimed at respectively; Described input optical signal is a linearly polarized light, and the polarization direction of described linearly polarized light is consistent with the fast axle or the slow axis of described photo-coupler.

8. method as claimed in claim 7 is characterized in that if the optical signal power I that receives ₄Non-vanishing, and the linearly polarized light polarization direction of input is consistent with the photo-coupler slow axis, then detects the output power I of slow axis and fast axle respectively at the 4th port (4) _4xAnd I _4y, adjust coupling device earlier to fast shaft power I _4yBe zero, adjust coupling device again to slow axis output power I _4xBe zero.

9. method as claimed in claim 6 is characterized in that described photo-coupler is a monomode coupler, and described input optical signal is circularly polarized light or linearly polarized light.

Images