WO2002091065A1 - A method for searching and tracking wavelength with variable step-length - Google Patents

Abstract

The present invention provides a method for searching position in the optical spectrum and tracking wavelength with variable step-length. During the searching, the longer searching step-length with increasing rate will be used, if power of light detected has not achieved continually predetermined level in twice. When the predetermined power of light is detected, step-length is modified, and searching with shorter step-length. The method in present invention has advantages in searching position in the optical spectrum, such as more rapid, accurate, and without increasing cost.

Description

 Method for searching, positioning and tracking light wavelength

 The invention relates to the technical field of automatic control, and more particularly, to a method for searching and locating and tracking the wavelength of light waves with variable steps. Background technique

 In the prior art, there are two methods for locating and tracking the wavelength of light waves. The first method is the hardware matching method. Since the wavelength of the light emitted by the laser is fixed, an optical filter of the corresponding wavelength is selected according to this wavelength. A filter is a passive filter, which can only filter light with a wavelength that matches. However, during the transmission of light, the wavelength of the light will change to a certain extent due to changes in the degree of blast or fiber bending. The light filtered by this fixed optical filter is damaged to a certain degree. Since this method does not require software to implement automatic control and control, it only needs proper hardware matching. Its disadvantages are obvious, namely poor self-adaptability and narrow range, especially when the signal is weak, it will become quite unreliable.

 The second method in the prior art is to use an active tunable optical filter, through a fixed step size (here, the step size refers to the amplitude of the voltage adjustment of the second drive tunable optical filter), Jiesso Locate at the signal, and then use this voltage as the operating voltage to drive the tunable optical filter. During the work, slightly change the operating voltage to drive the tunable optical filter at certain intervals to achieve The purpose of dynamically adapting to changes in light wavelength. The specific search and tracking process is as follows:-

1: Apply a driving voltage to the optical filter, record the optical power value after passing through the optical filter, and then add or subtract a step value to the driving voltage according to the search direction, drive the optical filter again and record this time The optical power value after passing through the optical filter.

 2: Repeat the above process. After the recorded value exceeds three, the condition judgment of the recorded value will be started, and every subsequent increase of the recorded value will be judged once. The condition judgment is performed as follows: Take an i recorded value, and then compare it with the two recorded values before and after. If it is greater than the two recorded values before and after, a second judgment is made; otherwise, no Make a second judgment and return to process 1 to continue;

The second judgment is made as follows: A ratio is calculated for the intermediate recorded value. If the two recorded values before and after are less than this value, record this value ^: the driving voltage value here, and then perform the third judgment The third judgment is performed as follows: Compare the recorded power value with the stored maximum power value. If the power value is greater than the stored maximum power value, use this value to replace the stored maximum rate. Value, otherwise, go back to Ning 1 to continue;

 3: In this way, repeat the above process until the driving voltage exceeds the given range, the search ends, and then the voltage at the maximum power will be driven ^: filter, enter the dynamic tracking process 4;

 4: The dynamic tracking process is as follows-

4A- First judge whether the time interval is less than, if it is, start the tracking process and enter 4B; if not, judge whether the power has changed. If the power does not change, repeat 4A. If there is a change, modify the time interval and start the tracking process. Go to 4B.

 4B: The current voltage point is taken as the center point, and the tracking step value is used to adjust the amplitude to make the optical filter swing in a certain direction. If the power value after the strike is greater than the power value of the current operating point, it will continue to swing in that direction. If the power value after the swing is smaller than the power value of the current working point, then the direction swing is changed. '

 4C: For the second time, compare the power after swinging with the power value of the current working point. If the power-rate value after selection is less than the current working point value, decrease the tracking step value, change direction, and continue from 4B starts to repeat until the tracking step value stabilizes at 1, and ends the tracking, and enters into 4D; if the power value after swing is greater than the power value of the current operating point, increasing the tracking step value continues to swing in this direction, and enters 4B repeat;

 4D: _ Repeat from 4A: The above process.

 The disadvantage of this # method is that although the second method is used to solve some aspects of the first method, it also adds a new unreliable factor. That is, when the optical signal is relatively weak, the signal may not be searched. Or search for an error point.

 The object of the present invention is to provide a method that can quickly and accurately locate the wavelength of light waves. Summary of the Invention

 In order to solve the contradiction between fast and accurate, the present invention proposes a method for searching, positioning and tracking the wavelength of light waves. The key is to choose different step sizes according to different positions in the search process, that is, The present invention provides a variable step-size search, positioning, and tracking wavelength of light waves: a "¾" method, that is, through a large amount of data analysis, it can be found that the optical power of the optical signal is the maximum when the optical signal completely overlaps with the optical filter, and the optical power when the optical signal does not completely overlap It will be reduced, the optical power changes within a certain bandwidth range between full re-overlap and non-overlap, but the optical power change is small when there is no overlap. According to this characteristic of the optical filter, the power change cannot reach When a certain amplitude is reached, a fast search method with a large step size is adopted, and when the power change reaches a certain amplitude, the step size is modified, and a small step size search method is used.

The implementation of the method provided by the present invention has achieved good results in the application of searching and locating the wavelength of light waves, which not only satisfies the fast search process requirements, but also ensures accurate and error-free optical signal processing without increasing processing costs. Overview of the drawings

 In the following, the features of the present invention will be further described with reference to the accompanying drawings and actual examples. In the drawings-Figs. 1A and B are a flowchart of the method of the present invention. The best embodiment of the present invention

 The following describes the features of the method of the present invention with reference to FIGS. 1A and B in combination with a specific embodiment of the method of the present invention. In the flowchart shown in FIG. 1, the meaning of each symbol is described as follows:

 value [n]: the optical power value at the current point when searching;

 value [n— 1] t The optical power value of the previous point during the search;

value [η + 1] ' _: the optical power value of a point during search;

 power [n]: optical power value at the time of It when tracking;

 power [n-i]: the optical power value of the previous point during tracking;

 maxpower: maximum value in a small range during a fine search;

 MAXPOWER: the maximum value in the entire range;

 powerl: power value of the current center point during tracking;

 power2: the power value of the current swing point during tracking;

 The specific implementation process is described as follows:

 1: Apply a driving voltage to the optical filter (box.101), record the optical power value after passing through the optical filter at this time (box 102), and then add or subtract a driving value to the driving voltage according to the cable direction (box 125), drive the optical filter again, and record the optical power value after passing through the optical filter again.

2: Repeat the above process. After more than three recorded values (block 103), start to make conditional judgments on the recorded values, and make a judgment every time after adding one more recorded value. The condition judgment is performed as follows: take a record value, and then compare it with the two previous and next record values (block 105); if it is larger than the two previous and next record values, then perform a second judgment (block 106); otherwise , ^¾ Do not perform the second judgment, return to J "Process 1 (Go to box 101)-continue to fi; The second judgment is performed as follows: Give the intermediate record value. Calculate a value proportionally (R e value [ n]), if there are two previous and next recorded values (value [n— 1], value [n + 1]) as long as one of them is less than this value, it is the first time to satisfy the ^ condition, and two steps back at this point Long, and use the backing point as the starting point, greatly reduce the step size value (block 107)., Start the small step fine search process, enter 3; otherwise return to process 1 (block 101) to continue.

3: Small step size and fine search process: First determine that the number of fine searches is not reached (block 108). If so, restore the step size value at the beginning and make a second judgment, see process 4 (box '112, box 114, and (Box 116). If it arrives, each time it adds a record point, it is compared with the previous and next record values. If it is greater than the previous and next record values (box 110), then the maximum value record in the small step size search process is refreshed ( (Block 111), otherwise, the record is not refreshed, and the process 3 (block 108) is continued.

 4: The Z-th judgement is performed as follows: calculate a value proportional to the maximum recorded value of the power '(maxpower ^ K), if two consecutive recorded values appear within N i before and after the recorded values are less than This value (box 112) (Note: N is a set constant), that is, the condition is satisfied for the first time, and then this power maximum value is compared with the maximum power saved in the entire process (box 114). If it is greater than the maximum value, the maximum value and related records are refreshed (block 116), otherwise the records are not refreshed. Then, restore the step size at the beginning, exit the small step fine search process (box 109), return to process 1 (box 101) and continue until the search process ends within the specified range, and the voltage at the maximum power will be obtained Value-driven light 'filter, enter the tracking process (block 113);

 • 5: The tracking process is as follows:

 5A: First determine if the time interval is less than (block 115), if it is, start the tracking process, see 5B, if not, determine whether the power has changed (block 117), if there is no change, return to box 115, repeat 5A, if the power changes, modify the time interval, start the tracking process (box 115) ', and enter 5B.

 5B: The current voltage point is taken as the center point, and the tracking step value is adjusted to make the optical filter swing in a certain direction. If the power value after the swing is greater than the power value of the current operating point (box 120), continue to This direction swings (block 124), and if the power value after swinging is smaller than the power value of the current operating point, then the direction swings (block 123).

5C: Compare the power value after the second swing (po _We r2 with the power value of the current operating point

(powerl), if the pendulum 'power value is less than the current operating point of the dynamic power value e _P ower2 <pooerl), the step value is decreased tracking, change direction (block 122), and returns 5B (block 119) is repeated, Until the tracking step value stabilizes at 1, end the tracking and enter 5D;

 If the power value after the swing is greater than the power value of the current operating point, increase the tracking step value to continue swinging in that direction (block 124), and enter 5B to repeat;

 5D: Repeat the process from 5A. Industrial applications

In order to study the practical effect of the present invention, in an experimental transmission device equipped with an OTF-610 tunable active optical filter, when the second method of the technology described in this specification is applied to search the wavelength of light waves, it is found that When the light signal is very small, for example, when it is close to 46 dB, the signal cannot be searched in some waves and long positions, and some false signals are sometimes searched. When using the method of the present invention, the optical signal is also very weak, However, when it is close to a 50db, the optical signal can still be correctly captured at any position, and the scope of application is improved without changing the hardware configuration. -

Claims

Claim  1. A method for searching, positioning, and tracking light wavelengths, including a searching and positioning process and a tracking process, characterized in that, during the searching process, if the detected optical power changes twice do not reach a certain amplitude, a large step size is used to quickly Search method, and modify the step size when the optical power change reaches a certain amplitude, use the 'small step size fine search method'.  2. The method according to claim 1, wherein the search and positioning process comprises the following steps:  1) According to a search direction, record the optical power values after passing through the optical filter at three different driving voltages, and the three different driving voltages differ by one step from each other.  2) Under the condition that the current driving voltage base ^ i is increased or decreased by a certain step, record the optical power value through the optical filter, and compare the recorded value with the two previous and next records. If it is greater than the previous two If the recorded values are all large, step 3) is performed; otherwise, return to step 1);  3) Calculate a value proportionally from the middle record value. If only one of the two previous and next record values is less than this value, it is the first time that the condition is satisfied, and two steps are made at this point, and the back point is used. As a starting point, a large small step size value starts a small step fine search process, and executes the small step fine search process, that is, step 4), otherwise returns to step 1);  4) First judge whether the number of times of the fine search is less than, if it is, then restore the step value at the beginning, make a second judgment, and proceed to step 5); if it is not, every time you add a record point, it will be compared with the previous two Compare the two record values. If it is larger than the two previous and next record values, refresh the maximum value records in the small step and fine search process; otherwise, do not refresh the records and repeat this step;  5) Calculate a value proportional to the recorded value of the maximum power value. 'If two consecutive recorded values are less than this value (N is a set constant), the condition is met for the first time. Then, compare this power maximum value with the maximum power value saved in the entire process. If the maximum value is greater than the maximum value, 'the maximum value and related records are refreshed, otherwise the records are not refreshed. 'Then, restore the step value at the beginning, step back to the small step size search process, and return to step 1) Continue until the search process ends within the specified range to obtain the voltage value at the maximum power. Drive the optical filter , Into the tracking process;  3. The method according to claim 1 or 2, wherein the tracking process comprises the following steps:  1) First determine whether the time interval has not arrived. If the time interval has expired, perform step 2) If the time interval has not expired, determine whether the power has changed. If there is no change, repeat step 1). 'If there is a change, correct it. Time interval, start the tracking process, and proceed to step 2); 2) The current voltage point is taken as the center point, and the tracking step value is used to adjust the amplitude to make the optical filter towards a certain Swing in the direction, if the power value after the swing is greater than the power value of the current working point, continue to swing in that direction; if the power value after the swing is less than the power value of the current working point, then swing in the other direction;  3) Compare the power value after swinging with the power value of the current working point for the second time. If the power value after swinging is less than the power value of the current working point, then decrease the tracking step value and change the direction. Continue from step 2) Repeat until the tracking step value stabilizes at 1 and end the tracking; if the power value after swinging is greater than the power value of the current working point, increase the tracking step value and continue to swing in this direction, and re-enter step 2).