JPS61151611A - By-pass optical switch - Google Patents

Abstract

PURPOSE:To make a device small-sized, to reduce the power consumption and to improve the reliability of the device by connecting two sets of single pole double throw optical switches consisting of polarizing beam splitters for separation and synthesis, nematic liquid crystal cells, and rectangular prisms to reduce a moving part. CONSTITUTION:A voltage VH is impressed to a liquid crystal cell 19, and a P-polarized light 21 which is inputted from an optical fiber 3 and is separated by a polarizing beam splitter 11 for separation and is transmitted through the liquid crystal cell 19 is totally reflected on a rectangular prism 16 and is synthesized with the other S- polarized light 22 by a polarizing beam splitter 12 for synthesis and is outputted from an optical fiber 4. If a trouble occurs in a terminal and a low voltage VL is impressed to liquid crystal cells 19 and 20, the P-polarized light 21 and the S-polarized light 22 are converted to beams of polarized light of each other and are synthesized by the splitter 12 and are separated by the splitter 13 and are restored to original polarized light by the liquid crystal cell 20 and are synthesized by a splitter 14 and are outputted from an optical fiber 6. Consequently, the moving part is reduced because two single pole double throw switches are connected in series, and the device is made small-sized, and the power consumption is reduced, and the reliability is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides 1. communication terminals and information processing terminals installed within a limited area, such as within the same building or within the same factory premises, by using original fiber communication. Optical LAN (optical LAN) connects in a ring through lines and performs communication and information processing.
cal Area Network).

This invention relates to a bypass optical switch that bypasses an optical transmission line when a terminal fails.

[Conventional technology]

FIG. 6 is a block diagram showing a conventional bypass optical switch. FIGS. 6(2) and 6(03) respectively show two states in which the bypass optical switch is switched.

In the figure, 1 is a trapezoidal prism, 2 is an electromagnet that moves the trapezoidal prism 1, 3.5 is an input source fiber, 4.6 is an output optical fiber, and 7 and 9 are each input source fibers 3 and 5.
A convergent rod lens that converts the incident light from the
Numerals 8 and 10 are convergent rod lenses that converge parallel light onto the output optical fibers 4 and 6, respectively. A conventional bypass optical switch has a mechanical structure, and consists of two converging four-wire/double switches at a predetermined distance in the direction of the original axis.7. A one-to-one imaging optical system is formed in which the input optical fiber 3 and the output optical fiber 6 are respectively connected to one end of each convergent rod lens 7.10.

In the bypass optical switch configured as described above, as shown in FIG. 6(A)K, a current is supplied to the electromagnet 2, and the electromagnet 2 is inserted into the gap between one trapezoidal prism 1t and two convergent rod lenses 7 and 10. In this state, the light input from the input optical fiber 3 and converted into a parallel element by the convergent rod lens 7 is reflected by a reflective film deposited on the end face of one trapezoidal prism l, and then enters the convergent rod lens 8. and output to the output optical fiber 4. On the other hand, the light input from the input optical fiber 5 and converted into parallel light by the convergent rod lens 9 is reflected by a reflective film deposited on the end face of the trapezoidal prism 1, and then enters the convergent rod lens 10 and output. The optical signal 7 is output to the optical system 6.

Next, as shown in FIG. In this state, the nine beams inputted from the original input fiber 3 and converted into parallel beams through the convergent rod lens 7 travel straight, enter the convergent rod lens 10, and are outputted to the output optical fiber 6.

On the other hand, the light inputted from the original input fiber 5 and converted into parallel light by the convergent rod lens 9 is transmitted through the trapezoidal prism 1
Although the light is reflected by a reflective film deposited on the end face of the light, it is not output to the output optical fiber 6 because its optical axis is offset from the optical axis of the imaging optical system.

Connect the above bypass optical switch to 9, for example, a ring-shaped optical LAN.
In the case of applying to Each is used by connecting to a transmitter. Under normal terminal operation, the bypass optical switch
As shown in the lcS figure, input source fiber 3 and output fiber 7
The IPA 4 is coupled, and the input optical fiber 5 and the output optical fiber 6t are coupled. In a state where the terminal is out of order, the bypass optical switch connects the input optical fiber 3 and the output optical fiber 6t, as shown in FIG. 6), thereby bypassing the failed terminal.

[Problem that the invention seeks to solve]

In traditional bypass optical switches like the one above.

Since the trapezoidal prism 1 was moved using the electromagnet 2, the installation was large and the power consumption was large, and insertion loss and crosstalk increased due to damage to the trapezoidal prism 1 and loosening of mechanical parts due to vibration. However, there was a problem that the operating life was shortened. In addition, since each end face of one trapezoidal prism 1 and each converging rod lens 7 to IO is exposed to the atmosphere, a reflective film is deposited on the end face of one trapezoidal prism 1, and a film is deposited on the end face of each converging rod lens 7 to 10. There were four points where the reflective coating film corroded due to the effects of temperature, gas, etc.

The present invention has been made to solve these problems, and an object of the present invention is to obtain a bypass optical switch that can reduce the size of the device, reduce power consumption, and improve reliability.

[Means to resolve the gap]

The bypass optical switch according to the present invention includes a liquid crystal cell filled with a nematic liquid crystal used as a switching element, and a separate polarized beam that separates linearly polarized light input into the liquid crystal cell and makes it gravity into two orthogonal polarized elements, or that combines the polarized light. a splitter and a polarizing beam splitter for combining;
Each convergent rod lens is connected to the input optical fiber and the output optical fiber, and converts the signal light into parallel light, or condenses the parallel light, and the optical path of one of the two orthogonal polarized lights. Two single-pole, double-throw optical switches configured with a right-angle prism that can be bent at right angles are connected in series.

[Effect]

In the bypass optical switch of the present invention, a liquid crystal cell is used as a switching element, and the optical path can be switched simply by switching the voltage applied to the liquid crystal cell, and there are no moving parts unlike conventional mechanical switches. Because there is no carbon, it has a long life and can reduce power consumption. Further, since the converging rod lenses, the separating polarizing beam splitter, and the combining polarizing beam splitter, which are the component parts, can be made smaller, the device can be made smaller. Furthermore, the liquid crystal cell, each converging condolens 9 polarizing beam splitter for separation, and a polarizing beam splitter for combining.

Since the end faces of the input optical fiber and the output optical fiber are fixed to each other using an adhesive, each end face is not exposed to the atmosphere and has excellent moisture and corrosion resistance.

〔Example〕

FIG. 1 is a block diagram showing a bypass optical switch which is an embodiment of the present invention, and each reference numeral 3 to IO is exactly the same as the conventional switch shown in FIG. 6 above.

11.13 is a polarizing beam splitter for separation, 12゜14
is a polarizing beam splitter for synthesis, 15 to 18 are right angle prisms, and 19.20 rotates the plane of polarization of the incident linearly polarized light by 90' by applied voltage v1 or vH and transmits it.
Or a liquid crystal cell filled with a nematic liquid crystal that transmits the liquid without being rotated, 21 denotes each separating polarizing beam splitter 11.13 and combining polarizing beam splitter 12.1.
P-polarized light 22 is linearly polarized light parallel to the incident plane of 4, and S-polarized light 22 is linearly polarized light perpendicular to the incident plane of each separating polarizing beam splitter 11.13 and combining polarizing beam splitter 12.14. Figure 1 (2) and [F]).

This figure shows two states in which each liquid crystal cell 19, 20 is switched, and each of these modes is exactly the same as in the case of FIG. In each such embodiment, each liquid crystal cell 19.20
Assume that the same voltage is applied to both.

In the bypass optical switch of the present invention configured as described above, first, the state shown in FIG.

Convergent rod lens 7 is input from input fiber 3
The light converted into parallel ft is separated into P polarized light 21 and S polarized light 22 by the separating polarizing beam splitter 11, and then the P polarized light 21 is totally reflected by the right angle prism 15 and its traveling direction is bent by 90 degrees. The S-polarized light 22 travels straight and enters the liquid crystal cell 19 at right angles. At this time, liquid crystal cell 19
When frequency f and voltage vH are applied to , as will be explained in detail later, the polarization plane of the incident linearly polarized light is transmitted without changing, so the P polarized light 21 that has passed through the liquid crystal cell 19 is totally reflected by the right angle prism 16. The light is combined with the S-polarized light 22 transmitted through the liquid crystal cell 19't by the combining polarization beam splitter 12, and this combined light enters the convergent rod lens 8 and is output to the source fiber 4 for output. Based on the same operating principle, light input from the input optical fiber 5 is output to the output optical fiber 6.

Next, see the steps in Figure 1 (in case a failure occurs on the terminal).
In the state shown in , the light input from the input optical fiber 3 and converted into parallel light by the convergent rod lens 7 is separated into P-polarized light 21 and S-polarized light 22 by the 1-separation polarization beam splitter 11. rear.

The P-polarized light 21 is totally reflected by the right-angle prism 15 and its traveling direction changes, and the S-polarized light 22 travels straight and enters the liquid crystal cell 19 perpendicularly. At this time, the frequency f and the voltage v are applied to the liquid crystal cell 19.
When Lt- is applied, the polarization plane of the incident linearly polarized light is rotated by 90'' and transmitted as will be explained in detail later, so the linearly polarized light transmitted through the liquid crystal cell 19 becomes P polarized light 2.
1 is converted to 5 (iiJjt, 22, i9, S polarized light 22 is converted to P polarized light 21. Of these, S polarized light 22 is totally reflected by the right angle prism 16, and S polarized light 22 is also converted to P polarized light.
(The light converted to 1m element 21 is combined with the polarizing beam splitter 12 for combining, and this combined light is input to the polarizing beam splitter 13 for separating. After being separated again into P polarized light 21 and S polarized light 22 by the beam splitter 13, the S polarized light 22
is totally reflected by the right angle prism 17, and P polarized light 21 and S
(One light 22 is perpendicularly incident on the liquid crystal cell 20. At this time, the same voltage as the liquid crystal cell 19 is applied to the 1g crystal cell 20, so based on the same operating principle, the P polarization jt, 21
is converted into S-polarized light 22, and S-polarized light 22 is converted into P-polarized light 21, respectively. Of these, the P-polarized light 21 is totally reflected by the right-angle prism 18, and combined with the light converted from the P-polarized light 21 to the S-polarized light 221fC by the polarizing beam splitter 14, and this combined light is passed through the converging rod lens IOK. The light is input to the source fiber 6 for output. In addition, in Figure 1)
In the state shown in , the light input from the input optical fiber 5 is emitted in a direction perpendicular to the combined light incident on the convergent rod lens IO, based on the same operating principle, and is not output to the output optical fiber 6. .

In the embodiment of the invention shown in FIG. 1, each input optical fiber 3, 5 and each output optical fiber 4.6 are connected to each liquid crystal cell 19, 20 and each separating polarizing beam splitter 11.
13 and the polarizing beam splitter for synthesis 12, 14, and each of the right angle prisms 15 to 58 are bonded to one surface of the composite glass block, that is, one surface of the downward direction shown in FIG. Since the applied voltage vL can be reduced to zero in principle, the space utilization rate of the device configuration is high, and there is no need to apply voltage vL to each liquid crystal cell 19, 20 when a failure occurs in the terminal. Each is superior in terms of driving conditions.

FIG. 2 is a block diagram showing a bypass optical switch according to another embodiment of the present invention, and each reference numeral 3 to 22 is the same as that explained in FIG. 1 above. Figure 2 (2) and [F]
) is each applied voltage vL in (2) and ) of FIG. 1,
This figure shows a state in which vH is reversed and applied to each liquid crystal cell 19, 20, and this bypass optical switch connects input optical fibers 3. The convergent rod lens 7, the original output fiber 6, and the convergent rod lens 10 are connected to each liquid crystal cell 19, 2.
0. Each separation polarizing beam splitter 11, 13. Each combining polarizing beam splitter 12.14. The rectangular prisms 15 to 18 are connected to each other so as to face each other via a composite glass block. Note that the operation is the same as that shown in FIG. 1 above, so a description thereof will be omitted.

By the way, since the above-mentioned bypass optical switch according to the present invention has a configuration in which two single-pole double-throw optical switches are connected in series, when the optical path length becomes long, insertion due to the aberration of each convergent rod lens 7 to 10 occurs. Loss is a problem, but each converging rod lens 7-100 has a diameter of 2 w.
i. Since the length is about 6 m, the beam diameter of the parallel light converted by each converging rod lens 7 to 10 is 2 degrees or less, and each of the polarizing beam splitters 11 and 13 for separation and the polarizing beam splitter for combining 12,14. Since the length of one side of each of the right angle prisms 15 to 18 can be reduced to about 31111, the optical path length of the liquid length in this case is 24 degrees of reduction, so there is almost no increase in loss due to aberration, and , it passes through each liquid crystal cell 19.20 twice, but in this case, the light absorption in each liquid crystal cell 19.20 is mainly due to the transparent electrode material, and the material is s
By using a ro membrane, the transmission loss for two pieces can be reduced to 0.
The coupling loss of each convergent rod lens 7 to 10 is about 0.4 dB, and the allowable loss is 0.3 dB due to the dimensional accuracy of each separating and combining polarizing beam sinter 11 to 14. Considering the degree of crosstalk, crosstalk from the input optical fiber 5 to the output optical fiber 4 is important for zero-order crosstalk that can reduce the total insertion loss to 1.5 dB or less. In an optical switch, two single-pole, double-throw optical switches are connected in series, and in principle, an input optical fiber 7 and an output optical fiber 7 are connected in series.
Although it is configured completely separate from the Aipa 4, in reality.

Each separating and combining polarizing beam splitter 11 to 14,
Each right angle prism 15-18. Since there is end face reflection at each liquid crystal cell 19.degree. 20, etc., the brightness is about -80 dB, and this value is superior to the above-mentioned conventional mechanical bypass optical switch.

FIG. 3 is a cross section showing an embodiment of a liquid crystal cell which is a switching element of a bypass optical switch according to this invention.
This is an iis composition diagram. In the figure, 23 is a transparent electrode such as an sro film, 24 is a glass substrate on which the transparent electrode 23 is deposited, 25 is a spacer made of a material such as a polymer compound, and 26 is a P-type nematic liquid crystal molecule. In this liquid crystal cell, in the state shown in FIG. 2 (2) where lEEyL is applied, the alignment direction of the long axis of the P-type nematic liquid crystal molecules 26 is changed by diagonal deposition of a SiOx film or rubbing with cotton cloth. This is a twisted nematic cell (TN cell) configuration in which the substrates 24 are twisted by 90 degrees. In the state shown in FIG. 3(2), if the plane of polarization of the linearly polarized light incident on the P-type nemadec liquid crystal molecules 26 is made parallel or perpendicular to the alignment direction of the long axis, the polarization plane of the P-type nemadec liquid crystal molecules 26 will be The torsion K therefore rotates and the 0th order K rotates T□ degrees 90' between the input and output surfaces.
, when this liquid crystal cell is applied with Kt pressure vH, as shown in FIG. 3(B).
Since this is a P-type nematic liquid crystal cell as shown in the state shown in K, the long axes of the P-type nematic liquid crystal molecules 26 are oriented in the direction of the electric field, so that light is transmitted without changing the plane of polarization.

FIG. 4 is a cross-sectional configuration diagram showing another embodiment of a liquid crystal cell which is a switching element of a bypass optical switch according to the present invention, in which reference numerals 23 to 26 are used.

This is the same as that explained in FIG. This liquid crystal cell has a shape 11! shown in FIG. 4(A)K. il, P-type nematic liquid crystal molecules 26 are obliquely deposited or rubbed so that their long axes form a tilt angle ψ of several orders of magnitude with respect to the glass substrate 24, and the glass substrate 240 is set to have a tilted orientation on both sides. At the same time, the orientation angle θ of the long axis of the P-type nematic liquid crystal molecules 26 is set to 45 with respect to the polarization plane of the incident linearly polarized light.
@Kushi, it has a π cell configuration using the condition that the phase difference δ of two orthogonal polarized lights is π.

Figure 5 is a diagram showing the operating principle of a liquid crystal cell with the π cell configuration shown in Figure 4. 27 is linearly polarized light with a polarization plane in the X-axis direction. The long axes of the P-type nematic liquid crystal molecules 26 are aligned uniformly over the X-axis and the Y-axis.
It is oriented at an angle of 45 degrees with respect to the axis, and linearly polarized light 27 whose plane of polarization is parallel to the X-axis direction is incident on it in biaxial directions.

At this time, when the electric field components in each of the X-axis and y-axis directions are Ez t Ey in oz(d), Ez*Ey has the following relationship.

However, E is the field strength, and Δn is the orthogonal two-wave field strength.
d is the refractive index difference, d is the thickness of the liquid crystal layer, and λ is the wavelength.

Depending on the value of the phase difference δ, the light of the linearly polarized light 27 propagates in two axial directions, and the polarization state becomes an ellipse of 2 circles or an ellipse.

As each linear polarization changes, the direction of the linear polarization jt, 27 also changes. That is, by setting the values of Δn and d to appropriate values so that δ−π, the plane of polarization of the linearly polarized light 27 that passes through the liquid crystal cell can be rotated by 90″.

Next, when a voltage vH is applied to this liquid crystal cell, as shown in FIG. Therefore, the plane of polarization is transmitted without changing.

Incidentally, in the above description, the case where the bypass optical switch of the present invention is applied to a ring-shaped optical LAN is described, but the present invention is not limited to this, and can be applied to a bus configuration,
It can also be used in a loop-configured LAN.

〔Effect of the invention〕

As described above, the present invention uses a liquid crystal cell filled with a natural liquid crystal as a switching element in a bypass optical switch, and rotates the plane of polarization of incident linearly polarized light by applying a voltage to the liquid crystal cell. Two single-pole, double-throw optical switches that separate linearly polarized light into two orthogonal polarized lights or combine polarized light and switch the optical path are connected in series, so compared to conventional bypass optical switches, there are fewer moving parts. It eliminates this problem, makes the device more compact, and also achieves longer life and lower power consumption.
Furthermore, it has excellent effects such as reducing crosstalk and increasing reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a bypass optical switch which is one embodiment of the present invention, and FIG. 2 is a block diagram showing a bypass optical switch which is another embodiment of the present invention. FIG. 3 is a cross-sectional configuration diagram showing one embodiment of a liquid crystal cell which is a switching element of a bypass optical switch according to the present invention, and FIG. 4 shows another embodiment of a liquid crystal cell which is a switching element of a bypass optical switch according to this invention. The fifth factor is a diagram showing the operating principle of the liquid crystal cell having the π cell configuration shown in FIG. 4, and FIG. 6 is a diagram showing the configuration of a conventional bypass optical switch. In the figure, 3.5... input optical fiber, 4°6.
...Output optical fiber, 7-10...Converging rod lens, 11.13...Polarizing beam splitter for separation,
12.14... Polarizing beam splitter for synthesis. 15-18...Right angle prism, 19.20...Liquid crystal cell, 21...-p polarized light, 22...S polarized light, 23...
Transparent electrode, 24...Glass substrate, 25...Spacer, 26...P-type nematic liquid crystal molecules, 27...Linearly polarized light having a polarization plane in the X-axis direction. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (4)

[Claims] (1) In a bypass optical switch that switches optical paths between two sets of input optical fibers and output optical fibers using an external control signal, the output light from the input optical fibers is converted into parallel light, or A pair of convergent rod lenses that converge parallel light onto an output optical fiber, a polarizing beam splitter that separates the input light converted into parallel light by the convergent rod lenses into two orthogonal polarized lights, and a polarizing beam splitter for separating the input light into two orthogonal polarized lights. the orthogonal two separated by a polarizing beam splitter for
A liquid crystal cell containing a nematic liquid crystal that rotates the polarization plane of polarized light by 90 degrees using an externally applied voltage or transmits it without being rotated, and a synthesis polarized light that combines the linearly polarized light that has passed through this liquid crystal cell. a beam splitter to polarize and then combine the input light;
A bypass optical switch characterized in that two single-pole, double-throw optical switches each configured with a set of right-angle prisms that bend the optical path of one of the two orthogonal polarized lights at right angles are connected in series. (2) The liquid crystal cell is a twisted cell in which the orientation directions of the nematic liquid crystal sealed inside are twisted by 90 degrees on the inner surfaces of the incident side and the output side of two glass substrates through which incident light passes. - The bypass according to claim 1, characterized in that a nematic cell is used and the liquid crystal cell is installed so that the orientation direction of the nematic liquid crystal is parallel to or perpendicular to the polarization plane of the incident linearly polarized light. light switch. (3) The liquid crystal cell is arranged so that the orientation direction of the nematic liquid crystal sealed inside is parallel to the inner surfaces of two glass substrates on the incident side and the output side through which incident light passes. , when the linearly polarized light making an angle of 45° with the alignment direction of the nematic liquid crystal is incident, the thickness is 18 between the two transmitted polarized lights separated perpendicularly to the alignment direction.
A liquid crystal cell with a π cell configuration selected to produce a phase difference of 0° is used, and the liquid crystal cell is installed so that the alignment direction of the nematic liquid crystal is 45° with respect to the two orthogonal incident polarized lights. A bypass optical switch according to claim 1. (4) A patent characterized in that the convergent rod lens is bonded to one surface of a glass block made by gluing together the liquid crystal cell, the separating polarizing beam splitter, the combining polarizing beam splitter, and the right angle prism. A bypass optical switch according to claim 1.