CN102736182A - Planar waveguide-type opto-isolator - Google Patents

Abstract

The invention discloses a planar waveguide-type opto-isolator, which comprises a core layer, wherein the core layer comprises a first waveguide, a first directional coupler, an upper interference arm, a lower interference arm, a second directional coupler, a 1*2 coupler and a second waveguide which are successively connected, wherein the upper interference arm and the lower interference arm are arranged in parallel; the first directional coupler is also connected with a third waveguide of a semi-circular ring; the third waveguide is connected with a fourth waveguide; the first waveguide is an upstream signal input waveguide; the second waveguide is an input waveguide of a downstream signal and an echo signal; and the third waveguide of the semi-circular ring and the fourth waveguide can be used for outputting the echo signal. According to the planar waveguide-type opto-isolator disclosed by the invention, the echo signal can not be reversely output from the original input port. In addition, the isolator has a small insertion loss for the upstream signal and the downstream signal.

Description

The planar waveguide-type optoisolator

Technical field

The relevant a kind of optoisolator of the present invention is meant a kind of optical fiber communication midplane waveguide type single fiber bi-directional photoelectric device usefulness planar waveguide-type optoisolator of reflective isolation back and forth that is used for especially.

Background technology

In the optical fiber telecommunications system, semiconductor laser is reflective very responsive to returning, and the reflective meeting of this time causes the semiconductor laser unstable properties.Therefore, it is reflective to need optoisolator to isolate this time.

Mostly existing in the market optoisolator is classical optoisolator, as adopting Faraday magneto-optical rotating crystal type optoisolator, birefringece crystal type optoisolator, is used for the encapsulation of axis light electrical part.For planar waveguide-type (PLC; Planar Lightwave Circuit) photoelectric device, classical optoisolator is not easy of integration to be packaged in the device, and its main cause is that the size of isolator own is bigger; And isolator is placed perpendicular to optical propagation direction; Can increase the package dimension of device, the material of classical isolator is different with the material of planar waveguide-type photoelectric device in addition, has bigger insertion loss.

Be referred from waveguide type Mach-Zehnder interferometer (MZI, Mach-Zahnder interferometer) dual wavelength is had branch wave property preferably, adopt interferometer structure similar, combine coupling mechanism can realize the propagation of light wave specific direction again with it.The structure of Mach-Zehnder interferometer comprises two identical 50: 50 directional coupler I, II and two interference arms, and is as shown in Figure 1, interferes arm can cause the phase differential of two-beam ripple, utilizes two-beam to interfere at coupling mechanism II place, for dual wavelength λ ₁, λ ₂, form λ ₁Grow mutually, disappear λ at output terminal 8 mutually at output terminal 7 ₂Disappear mutually at output terminal 7, long mutually at output terminal 8, thereby realize the function of partial wave.

Yet the Mach-Zehnder interferometer is 2 * 2 type elements, can not realize the function of single fiber input single fiber output.Output terminal 7,8 through in the interferometer rear end increases by 1 * 2 coupling mechanism; Can realize the function of upward signal single fiber output; But for downgoing signal, destroyed long mutually, the condition that disappears mutually of Mach-Zehnder interferometer, made the Mach-Zehnder interferometer can't realize single fiber output.Therefore need improve interferometer.

As shown in Figure 2, at first for downgoing signal,, be 50: 50 two-beam ripple afterwards through 1 * 2 coupling mechanism partial wave by waveguide 9 inputs, be designated as E respectively ₇, E ₈, two light waves are complex amplitude information, comprise amplitude and phase place.For simplifying technology, directional coupler I, II adopt identical symmetrical structure (its splitting ratio no longer is 50: 50), the note wavelength X ₁, λ ₂Propagation constant in directional coupler I, II is respectively k _{λ 1}, k _{λ 2}, effective coupling distance of coupling mechanism is l, note α _λ=k _λL, waveguide 9 incident light waves are E ₀, satisfy:

$\left[\begin{array}{c}{E}_1\\ {\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="1206060928561.png,1206060928562.png"\; state="\{\{state\}\}">E</figure-callout>}}_2\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\&alpha;}& i\sin \mathrm{\&alpha;}\\ i\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}\end{array}\right]\left[\begin{array}{cc}\exp \left[\mathrm{i\&beta;}(L+\mathrm{\&Delta;L})\right]& 0\\ 0& \exp \left(\mathrm{i\&beta;L}\right)\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\&alpha;}& i\sin \mathrm{\&alpha;}\\ i\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}\end{array}\right]\left[\begin{array}{c}{E}_7\\ E_8\end{array}\right]---\left(1\right)$

Wherein β is for interfering the propagation constant of light wave in the arm.

If meet the following conditions:

ΔL·β _λ1＝2mπ+2α _λ1、ΔL·β _λ2＝2nπ+2α _λ2，m、n＝0，±1，±2... (2)

This moment is for λ ₁, E _{2, λ 1}=E ₀, E _{1, λ 1}=0, for λ ₂, E _{1, λ 2}=E ₀, E _{2, λ 2}=0, i.e. signal λ ₁Fully from port 2 outputs, signal λ ₂Export from port one fully.Explained that echoed signal can not get into upward signal λ ₁Passage in, therefore can oppositely not export from former input port, play the effect of isolation, simultaneously to downgoing signal λ ₂Zero-decrement passing through.

For upward signal, by waveguide 1 input at port one place, the light wave fields of incident is E ' ₀,

$\left[\begin{array}{c}{E}_7\\ {\mathrm{<figure-callout\; id="8"\; label="E"\; filenames="1206060928562.png"\; state="\{\{state\}\}">E</figure-callout>}}_8\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\&alpha;}& i\sin \mathrm{\&alpha;}\\ i\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}\end{array}\right]\left[\begin{array}{cc}\exp \left[\mathrm{i\&beta;}(L+\mathrm{\&Delta;L})\right]& 0\\ 0& \exp \left(\mathrm{i\&beta;L}\right)\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\&alpha;}& i\sin \mathrm{\&alpha;}\\ i\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}\end{array}\right]\left[\begin{array}{c}{E}_0^{\&prime;}\\ 0\end{array}\right]---\left(3\right)$

If meet the following conditions

ΔL·β _λ1＝2mπ+2α _λ1、ΔL·β _λ2＝2nπ+2α _λ2，m、n＝0，±1，±2...

sin(2α _λ1)＝0 (4)

This moment is for λ ₁, the splitting ratio of directional coupler I, II is 0: 100, the characteristic of this directional coupler is port one input, port 4 outputs; Port 2 inputs, port 3 outputs, as shown in Figure 3.

This moment E _{7, λ 1}=E ' ₀, E _{8, λ 1}=0, promptly signal is fully from output terminal 7 outputs.So upward signal λ ₁When 1 * 2 coupling mechanism closes ripple, can not interfere, light wave is undamped.

Optoisolator is for upward signal λ in a word ₁Undamped passing through plays buffer action for echo; To downgoing signal λ ₂Zero-decrement passing through.

Optoisolator of the present invention just is being based on above analysis and calculating.

Summary of the invention

In view of this, fundamental purpose of the present invention is to provide a kind of to upward signal and downgoing signal has very little insertion loss and echoed signal played the planar waveguide-type optoisolator of buffer action.

For achieving the above object; The present invention provides a kind of planar waveguide-type optoisolator, and it includes sandwich layer, and said sandwich layer includes first waveguide, first directional coupler, parallel the going up of being provided with that link to each other successively interferes arm and interfere arm, second directional coupler, 1 * 2 coupling mechanism, second waveguide down; This first directional coupler also is connected with the 3rd waveguide of semicircular ring; The 3rd waveguide is connected with the 4th waveguide, and this first waveguide is the input waveguide of upward signal, and second waveguide is the input waveguide of downgoing signal and echoed signal; This first directional coupler and second directional coupler are in order to the lateral of light beam; Should go up the interference arm and interfere arm in order to introduce the coherent phase potential difference down, this 1 * 2 coupling mechanism is in order to partial wave and close ripple, and the 3rd waveguide of this semicircular ring and the 4th waveguide are in order to the output echoed signal.

Said 1 * 2 coupling mechanism comprises parallel upper arm and the underarm that is provided with.

Said first directional coupler and second directional coupler are 0: 100 coupling mechanism.

Said upward signal gets into isolator by first waveguide, and upward signal is interfered arm through getting into behind first directional coupler down, afterwards through getting into the underarm of 1 * 2 coupling mechanism behind second directional coupler, is finally exported by second waveguide; Said downgoing signal is imported by second waveguide, after the energy distribution through 1 * 2 coupling mechanism, respectively by upper arm and underarm transmission; Two paths of signals is interfered arm and is interfered arm down through getting into behind second directional coupler to go up, and there is phase differential in upper and lower interference arm, causes the change of two bundle signal phase information; Through behind first directional coupler, two-way light interferes again, satisfies for downgoing signal and interferes long mutually in first waveguide place; Disappear mutually in the 3rd waveguide place interference, downgoing signal is exported by first waveguide.

Said echoed signal disappears in first waveguide place interference mutually, and long mutually in the 3rd waveguide place interference, echoed signal is exported by the 3rd waveguide, gets into the 4th waveguide output afterwards.

Said first directional coupler, second directional coupler, 1 * 2 coupling mechanism and go up and interfere arm all to include curved waveguide with interfering arm down, the radius-of-curvature of this curved waveguide is all greater than 4mm.

The phase differential that planar waveguide-type optoisolator utilization of the present invention interferes arm to be introduced makes echo interfere at former input port place to disappear mutually, thereby can't oppositely export from former input port; In addition, this isolator has very little insertion loss to upward signal and downgoing signal.

Description of drawings

Fig. 1 is existing waveguide type Mach-Zehnder interferometer structure synoptic diagram;

Fig. 2 is improved waveguide type Mach-Zehnder interferometer structure synoptic diagram;

Fig. 3 is 0: 100 directional coupler beam propagation synoptic diagram;

Fig. 4 is a planar waveguide-type optoisolator plan view of the present invention;

Fig. 5 propagates figure for the upward signal of planar waveguide-type optoisolator of the present invention;

Fig. 6 propagates figure for the downgoing signal of planar waveguide-type optoisolator of the present invention;

Fig. 7 propagates figure for the echoed signal of planar waveguide-type optoisolator of the present invention;

Fig. 8 is the wherein a kind of structural representation that the present invention is based on silica-based planar waveguide-type optoisolator;

Fig. 9 is the cross section structure synoptic diagram of optoisolator of the present invention.

Embodiment

For ease of structure of the present invention and the effect that reaches are had further understanding, combine the accompanying drawing preferred embodiment that develops simultaneously to specify as follows at present.

Among the present invention the implementation of waveguiding structure and material can adopt following any: 1. structure adopts hole buried; Material is substrate with silicon; Substrate above-prepared silicon dioxide under-clad layer, the under-clad layer above-prepared is mixed the silicon dioxide sandwich layer of germanium, sandwich layer above-prepared silicon dioxide top covering; 2. structure adopts the ridged mode, and material is a substrate with silicon, preparation germanium silicon core layer on the substrate; 3. it is buried that structure adopts half hole, and material is substrate with the lithium niobate, and substrate top surface prepares doped titanium lithium niobate sandwich layer; 4. structure adopts silicon mode on the insulation course, and material is substrate with silicon, substrate above-prepared oxygen buried layer, oxygen buried layer above-prepared silicon core layer.With the 1st kind of mode is example, like Fig. 8 and shown in Figure 9.

Like Fig. 8 and shown in Figure 9, the perspective view of planar waveguide-type optoisolator of the present invention, that optoisolator comprises from the bottom to top successively is silica-based 20, under-clad layer 21, sandwich layer 22 are parallel to each other with the plane of top covering 23, four.As shown in Figure 4; Sandwich layer 22 of the present invention includes successively first waveguide 10 that links to each other, 0: 100 first directional coupler 12 (the circle dotted line indicates among Fig. 4), parallel going up of being provided with interfered arm 13 and interfered arm 14,0: 100 second directional coupler 15 (the circle dotted line indicates among Fig. 4), 1 * 2 coupling mechanism (it comprises parallel upper arm that is provided with 16 and underarm 17), second waveguide 11 down; The 3rd waveguide 18, the three waveguides 18 that first directional coupler 12 also is connected with semicircular ring are connected with the 4th waveguide 19.

First waveguide 10 is upward signal λ ₁Input waveguide, second waveguide 11 is downgoing signal λ ₂And echoed signal λ ₁The input waveguide of (identical) with the wavelength of upward signal; The effect of first directional coupler 12 and second directional coupler 15 is lateral of light beam; Satisfy formula (4), on to interfere arm 13 and the effect of interfering arm 14 down be to introduce the coherent phase potential difference, satisfy formula (2); The effect of 1 * 2 coupling mechanism is partial wave and closes ripple that the 3rd waveguide 18 of semicircular ring and the effect of the 4th waveguide 19 are output echoed signal λ ₁

As shown in Figure 5, the upward signal of planar waveguide-type single fiber bi-directional device of the present invention (being that laser instrument transmits) wavelength is λ ₁, downgoing signal (being that detector receives signal) wavelength is λ ₂Upward signal λ ₁Get into isolator by first waveguide 10, according to background knowledge, upward signal λ ₁Get into interference arm 14 down through first directional coupler, 12 backs, get into the underarm 17 of 1 * 2 coupling mechanism afterwards through second directional coupler, 15 backs, finally by second waveguide, 11 outputs.As shown in Figure 6, downgoing signal λ ₂By second waveguide, 11 inputs, after the energy distribution through 1 * 2 coupling mechanism, respectively by upper arm 16, underarm 17 transmission; Two paths of signals gets into upper and lower interference arm 13,14 through second directional coupler, 15 backs; Because there is phase differential in upper and lower interference arm 13,14, cause the change of two bundle signal phase information, again through behind first directional coupler 12; Two-way light interferes, for downgoing signal λ ₂Satisfy and interfere longly mutually at first waveguide, 10 places, the interference of the 3rd waveguide 18 places disappears mutually, so downgoing signal λ ₂By first waveguide, 10 outputs.The implementation of upper and lower interference arm 13,14 phase differential has two kinds; First kind of mode is through introducing the length difference Δ L of upper and lower interference arm 13,14; Length difference Δ L and phase delta phi satisfy Δ φ=Δ L * 2 π/λ; The second way will go up and interfere arm 13 or interfere arm 14 directly to be modulated down through phase modulation component.As shown in Figure 7, for the laser instrument echoed signal λ on the optical fiber link ₁, satisfy to interfere and disappear mutually at first waveguide, 10 places, interfere at the 3rd waveguide 18 places long mutually, so echoed signal λ ₁By the 3rd waveguide 18 outputs, get into the 4th waveguide 19 outputs afterwards, therefore can not get in first waveguide 10, thereby get rid of back reflective influence laser performance, play and isolate back reflective purpose.

The refractive index of sandwich layer is decided according to different needs, and its scheme of joining choosing mainly contains two kinds: 1. the refractive index contrast Δ is 0.75%, and waveguide is a rectangular waveguide, and the cross section lateral dimension is 6um * 6um, is used for the demand of conventional waveguide chip; 2. the refractive index contrast Δ is 1.5%, and waveguide is a rectangular waveguide, and the cross section lateral dimension is 4um * 4um, is used for the demand than miniature chip.

Directional coupler, 1 * 2 coupling mechanism and interference arm all include curved waveguide, and the radius-of-curvature of this curved waveguide can effectively reduce the loss that causes because of waveguide bend all greater than 4mm.Planar waveguide-type isolator and planar waveguide-type single fiber bi-directional device adopt identical materials and substrate, and the waveguide dimensions of substrate thickness, cladding thickness, sandwich layer is all identical, therefore integrated more easily and preparation.

Planar waveguide-type optoisolator of the present invention is to be directed against optical fiber communication with planar waveguide-type single fiber bi-directional photoelectric device, utilizes the phase differential of interfering arm to be introduced to make echo interfere at former input port place and disappears mutually, thereby can't oppositely export from former input port; In addition, this isolator has very little insertion loss to upward signal and downgoing signal.The present invention adopts ripe mixing integrated technology and plane wave waveguide technology, is that substrate, silicon dioxide are covering with silicon, and the silicon dioxide of mixing germanium is sandwich layer; Its mature preparation process; Structure is simpler, and size is little, adopts waveguide material and the substrate identical with planar waveguide-type single fiber bi-directional device; Easy of integration, be convenient to produce in batches.

The above is merely preferred embodiment of the present invention, is not to be used to limit protection scope of the present invention.

Claims (6)

1. planar waveguide-type optoisolator; It includes sandwich layer, it is characterized in that, said sandwich layer includes first waveguide, first directional coupler, parallel the going up of being provided with that link to each other successively interferes arm and interfere arm, second directional coupler, 1 * 2 coupling mechanism, second waveguide down; This first directional coupler also is connected with the 3rd waveguide of semicircular ring; The 3rd waveguide is connected with the 4th waveguide, and this first waveguide is the input waveguide of upward signal, and second waveguide is the input waveguide of downgoing signal and echoed signal; This first directional coupler and second directional coupler are in order to the lateral of light beam; Should go up the interference arm and interfere arm in order to introduce the coherent phase potential difference down, this 1 * 2 coupling mechanism is in order to partial wave and close ripple, and the 3rd waveguide of this semicircular ring and the 4th waveguide are in order to the output echoed signal.

2. planar waveguide-type optoisolator as claimed in claim 1 is characterized in that, said 1 * 2 coupling mechanism comprises parallel upper arm and the underarm that is provided with.

3. planar waveguide-type optoisolator as claimed in claim 1 is characterized in that, said first directional coupler and second directional coupler are the 0:100 coupling mechanism.

4. planar waveguide-type optoisolator as claimed in claim 2; It is characterized in that; Said upward signal gets into isolator by first waveguide; Upward signal is interfered arm through getting into behind first directional coupler down, afterwards through getting into the underarm of 1 * 2 coupling mechanism behind second directional coupler, is finally exported by second waveguide; Said downgoing signal is imported by second waveguide, after the energy distribution through 1 * 2 coupling mechanism, respectively by upper arm and underarm transmission; Two paths of signals is interfered arm and is interfered arm down through getting into behind second directional coupler to go up, and there is phase differential in upper and lower interference arm, causes the change of two bundle signal phase information; Through behind first directional coupler, two-way light interferes again, satisfies for downgoing signal and interferes long mutually in first waveguide place; Disappear mutually in the 3rd waveguide place interference, downgoing signal is exported by first waveguide.

5. planar waveguide-type optoisolator as claimed in claim 2 is characterized in that, said echoed signal disappears in first waveguide place interference mutually, and long mutually in the 3rd waveguide place interference, echoed signal is exported by the 3rd waveguide, gets into the 4th waveguide output afterwards.

6. planar waveguide-type optoisolator as claimed in claim 1; It is characterized in that; Said first directional coupler, second directional coupler, 1 * 2 coupling mechanism and go up and interfere arm all to include curved waveguide with interfering arm down, the radius-of-curvature of this curved waveguide is all greater than 4mm.

Images