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CN-115987387-B - Switch unit calibration method based on Benes network

CN115987387BCN 115987387 BCN115987387 BCN 115987387BCN-115987387-B

Abstract

The invention provides a method for calibrating switch units based on a Benes network, which comprises the following steps of selecting a switch unit of a middle stage of the network, selecting a route from an input port to an output port according to the switch unit, scanning the voltage of the tested unit to obtain the optimal working voltage of the tested unit, and sequentially calibrating all the switch units to the middle stage from the outermost stage of the switch unit. Because of the symmetrical nature of the Benes network, the left and right side switches are equivalent. According to the method for calibrating the switch unit, monitoring points do not need to be set in a network, the packaging difficulty of the large-scale integrated switch array is greatly reduced, the method can be matched with an automatic test scheme, and support is provided for subsequent large-scale manufacture and test of the optical switching chip.

Inventors

  • Ye dehao
  • HUANG XINYU
  • CHEN CHEN
  • CHU TAO

Assignees

  • 之江实验室

Dates

Publication Date
20260508
Application Date
20221206

Claims (7)

  1. 1. The switching unit calibration method based on the Benes network is characterized by comprising the following steps of: (1) Selecting a switching unit with an intermediate stage as a switching unit to be tested first in a Benes network, and selecting a route from an input port to an output port in a full-crossing state according to the switching unit; (2) Pre-biasing each switch unit in the route in a deflection cross state is set, and the light intensity of an input optical signal of an input port of the switch unit to be tested is as follows And the output port is connected with an optical power meter for detecting and outputting optical signals ; (3) The method comprises the steps of taking a switch cross state as transmission, taking the transmittance of the switch cross state as T, taking the through state as a crosstalk item X, scanning the voltage of a tested switch unit to obtain a point with the minimum output optical power as the point with the most deviated cross state of the switch unit under a selected cross path, namely the optimal working point of the through state of the switch unit; (4) Selecting a switch unit where the outermost stage is positioned in the Benes network as a tested switch unit, and selecting a route which is fully crossed from an input port to an output port according to the switch unit; (5) Repeating the step (2), setting the measured accurate cross state voltage of the intermediate-stage switch passing through the route, and setting the switch unit passing through the other crosstalk optical signal path of the test switch unit to deviate from the main route; (6) Starting from the outermost stage of switch in sequence, testing the inner stage of switch, selecting the switch unit closest to the intermediate stage in the Benes network as the tested switch unit, selecting a full-crossing route from the input port to the output port according to the switch unit, repeating the step (5), setting the tested switch to be an accurate crossing state voltage, setting the switch unit through which the other crosstalk optical signal path of the tested switch unit passes to be a state deviating from the main route, and finally calibrating the switch unit in sequence to obtain the optimal working voltage of the straight-through and crossing states of each switch unit at two sides of the intermediate stage.
  2. 2. The method of claim 1, wherein in the step (1), the routing of the full-crossing state selected in the Benes network includes all the switch cells without repetition, and the setting of +1V voltage to the switch cells can bias the switch cells to the crossing state.
  3. 3. The method of calibrating a switching unit based on a Benes network according to claim 1, wherein the pre-biasing biased in the cross state is set in the step (2), specifically, two parallel PIN structures with opposite polarities are designed for the upper and lower phase shift arms of the switch based on a Mach-Zehnder interferometer (MZI) structure to be in push-pull operation, and the initial phase of pi/2 is reduced on a phase shift arm, so that the initial state of the switching unit is in the intermediate state of cross and through, and the signs of the optimal operating points of the cross and through states are always correct and predictable.
  4. 4. The method of claim 1, wherein the transmittance T of a normal switching unit and the crosstalk term X in the step (3) are different by 20dB, which is 2 orders of magnitude, and each time the optical signal passes through a switch, the optical signal is multiplied by the state corresponding to the switch when calculating the output optical power.
  5. 5. The method of calibrating a switching unit based on a Benes network according to claim 1, wherein in step (3), an optical signal is outputted The transmission coefficient T of the tested unit is changed by the change of the voltage, so that the state of the crossing and the straight-through of the switch unit can be obtained by scanning the change of the voltage and the optical power of the tested unit.
  6. 6. The method for calibrating a switching unit based on a Benes network according to claim 4, wherein the output optical signal is The linear relation with the transmittance of the tested unit is that the pre-bias arrangement makes the signal light needed by the test as large as possible, and the state that the switch unit through which the other crosstalk optical signal path of the test switch unit passes is set to deviate from the main route makes the crosstalk light interfering the test result as small as possible, thereby outputting the optical signal Is in linear relation with the transmittance of the unit to be measured.
  7. 7. The method of claim 1, wherein in the step (5), the right and left sides of the Benes network are equivalent by input/output exchange due to the right and left symmetry of the Benes network.

Description

Switch unit calibration method based on Benes network Technical Field The invention relates to the technical field of silicon-based optoelectronic integration, in particular to a method for calibrating an opening unit based on a Benes network. Background With the increasing development of photonic integrated technology, the application of large-scale optical switching chips in cloud computing, high-performance computers and data centers is receiving more and more attention. However, due to the errors in the CMOS process, the initial states of the optical switch units at different positions in the whole Benes network are different, i.e. the optimal operating voltage of each optical switch needs to be tested and calibrated. The current mainstream calibration scheme is to set a monitoring port behind each switch unit or set monitoring ports at specific positions for optical detection, and the monitoring ports definitely exacerbate the subsequent optical and electrical packaging of the large-scale chip. The voltage calibration problem of the switch unit becomes one of factors limiting the number of I/O ports of the large-scale optical switching chip. Therefore, there is an urgent need for a scheme that can calibrate all switch units in a network only through characteristics and input/output ports of a Benes network without a built-in monitoring port. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a method for calibrating an opening light unit based on a Benes network, which aims to overcome the defects in the prior art. In order to achieve the above purpose, the present invention is realized by the following technical scheme: A method for calibrating a switch unit based on a Benes network comprises the following steps: (1) Selecting a switching unit with an intermediate stage as a switching unit to be tested first in a Benes network, and selecting a route from an input port to an output port in a full-crossing state according to the switching unit; (2) Setting pre-bias of deflection cross state for each switch unit on the route, inputting optical signal light intensity P i at the input port of the switch unit to be tested, and detecting output optical signal P o at the output port of the switch unit to be tested; (3) The method comprises the steps of taking a switch cross state as transmission, taking the transmittance of the switch cross state as T, taking the through state as a crosstalk item X, scanning the voltage of a tested switch unit to obtain a point with the minimum output optical power as the point with the most deviated cross state of the switch unit under a selected cross path, namely the optimal working point of the through state of the switch unit; (4) Selecting a switch unit where the outermost stage is positioned in the Benes network as a tested switch unit, and selecting a route which is fully crossed from an input port to an output port according to the switch unit; (5) Repeating the step (2), setting the measured accurate cross state voltage of the intermediate-stage switch passing through the route, and setting the switch unit passing through the other crosstalk optical signal path of the test switch unit to deviate from the main route; (6) Starting from the outermost stage of switch in sequence, testing the first stage inwards, selecting the switch unit closest to the intermediate stage in the Benes network as the tested switch unit, selecting a full-crossing route from the input port to the output port according to the switch unit, repeating the step (5), setting the tested switch to be an accurate crossing state voltage, setting the switch unit through which the other crosstalk optical signal path of the tested switch unit passes to be a state deviating from the main route, and finally calibrating the switch unit sequentially to obtain the optimal working voltage of each switch unit straight-through and crossing state at two sides of the intermediate stage. Specifically, in the step (1), the routing of the full-crossing state selected in the Benes network may include all the switch units without repetition, and setting the switch units to +1v can bias the switch units to the crossing state. Specifically, the pre-bias biased to the cross state is set in the step (2), namely, the upper and lower phase shift arms of the switch based on a Mach-Zehnder interferometer (MZI) structure are designed to be in a push-pull working mode by two parallel PIN structures with opposite polarities, and the initial phase of pi/2 is reduced on one phase shift arm, so that the initial state of the switch unit is in an intermediate state of cross and straight-through, and the sign of the optimal working point of the cross and straight-through state is always correct and predictable. Further, the transmittance T of one normal switching unit in the step (3) and the crosstalk term X differ by about 20dB, about 2 orders of magnitude, and each time the optical signal p