TW480331B - Multi-wavelength photodetector - Google Patents

Abstract

The present invention is a multi-wavelength photodetector to detect the optical characteristics of multi-wavelength light source in the fiber communication system; the detector disclosed by the present invention mainly completes detecting the light source by cooperating two optical filters, wherein one optical filter is a tunable optical filter to swap the light source in each communication channel one by one, and an optical filter having a fixed separation between communication channels is used as the pattern mask to convert it into the corresponding electrical signal according to the brightness of light source in accordance with the electro-optical signal conversion function of the photodetector, and then the electrical signal is processed to accomplish the goal of detecting the center wavelength of the light source in each communication channel, the uniformity of light source, or SNR.

Description

480331 [Scope of application of the invention] The present invention relates to a multi-wavelength light source monitoring system, and in particular, to monitor the optical characteristics of light sources of different wavelengths in an optical fiber communication system using a high-density wavelength multiplexing (DWDM) architecture. [Background of the invention] Muli has been used in the Wavelength DiviSlon Multiplexing (WDM) architecture used in optical fiber communication systems. Generally speaking, it contains thirty or more transmission channels, and each transmission channel

All use light sources of different wavelengths to transmit signals. It can also be said that the optical signals of each transmission channel have different wavelengths. Although WDM has the advantages of high capacity and high frequency bandwidth, in order to meet the future demand for greater communications, it is necessary to borrow By encrypting the interval of transmission channels, a high-density wavelength multiplexing (Dense Wavelength Dlvlslion Multiplexing: DWDM) architecture is formed in order to achieve a higher capacity and bandwidth optical fiber communication network. In addition to this, the speed of the Tinan Pass is also a feasible method currently used to increase capacity. According to the International Telecommunications Union (I n t e r n a t 丨 〇 n a 1

According to the proposal of Telecommunications Union (iTU), the channel wavelength interval of DWDM will be only 0.8 nm, that is, the frequency interval of 〇〇〇GHz, so the light source used in optical fiber communication must have a very narrow linewidth In other words, the wavelength of the light source must be limited to a narrow range of wavelengths, and the relative shift in the center wavelength of each transmission channel will be greatly reduced. In order to meet this stringent requirement, the light source # The technology of monitoring and stabilizing the output wavelength is also more eager. Of

480331 V. Description of the invention (2). Due to the relatively high spectral stability of the laser light source, a fiber optic communication system is the best light source in the system. In particular, the second body of the distributed feedback | private (Distributed Feedback Bragg: DFB) structure has a very narrow spectral width close to a single wavelength. Because of the two, the wide and wide 1 is often suitable for long distance, high capacity and Single-mode 丄 with a rate of $ β ^ in the modulated fiber-optic communication. Unconventional. The output wave of the DFΒ laser diode is different. By changing its bias voltage, it can also be adjusted to a small degree. Therefore, the optical fiber communication system with a micrometer measurement method for measuring the light source light source In the field of communication of China Supervision Fibers, the technology of “A 4%” and “Quality” f is the current optical fiber. In addition to this, in the application of surface light transmission (ie, light intensity), gradualness, such as: (Signal-to Nolse Ra; 50-channel digital data and optical signal to noise ratio measurement technology: ： Project 2 'is also this kind of multi-structured light I communication ^ Department: China Gas: Department is currently known-a kind of application _M frame mainly uses one: S :; optical characteristics of the system architecture It leads out-a small part :: uses .10 from a light source containing multiple different wavelengths to draw (swap) one of the different wavelengths:-, the scan is converted to electricity according to the intensity of the light source. * ': Light detection After being processed by the processor No. 12 of the state 12, the = sign passes through an operation control and telecommunications and then passes through a wavelength "; and then obtains various optical characteristics of the light source, at first ... in order to continue to monitor the light source of another wavelength. A uses known techniques of k types of construction, for example: in a paper published by NEC (κ.

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I 480331 V. Description of the invention (3)

Asahi eta 1., NEC Corporat i on, " Optical Performance monitor built into EDFA repeaters for WDM networks 丨 OFC '98 Technical Digest, pp. 318-319, 1 9 98.) Scanner (AOTF) to scan the light source and measure the overall system performance. However, due to the limitation of the optical characteristics of this AOTF, it is only applicable to the monitoring of the signal-to-noise ratio (SNR), the amount of transmitted light, and the cumulative number of channels. Another example that uses a single A0TF to monitor wavelengths in a scanning manner appears in a paper published by Pire 1 1 is (St Schmid et al. Pirellis, " High performance integrated acousto-opt ic channel analyzer1 ', OFC '97 Technical Digest., pp · 7-8, 1 9 9 7 ·), which uses the best specification A0TF (Sm m ··· to our knowledge, the best reported for a completely mono 1 ithi ca 1 1 y integrated device · ”) ° Admittedly, at least in terms of the side mode suppression ratio (SMSR), it is much better than our known specifications. Even so, we still find that it is not suitable for all communication conditions, and On the other hand, in order to overcome the measurement errors introduced by A0TF itself, more complicated control and calibration methods may be required. The one disclosed in "Figure 2" is another known multi-wavelength light source monitoring and control technology architecture. Before the light sources of different wavelengths are turned into the multi-wavelength multiplexer 15, a small part is extracted by the optical splitter 10, and these light sources of different wavelengths are all guided to 16 optical switch, the optical switch 16 under the control of a channel controller 17, one by one the light source directed through the filter Shu different wavelengths of a fixed channel spacing and the photodetector 8

Page 6 480331 V. Description of the invention (4) 1 2 'Convert the light source to an electrical signal' Through various operation control and electrical signal processing, after 1 3 'to obtain various optical characteristics of the light source, and then drive the channel control 1 7 Switch the channels of the optical switch 16 to continue to monitor the light source of the other channel. And the known technologies that apply this architecture, for example: In the introductory paper of NEC (T. Ono and Y. Yano, NEC Corporation, Key technologies for terabits / second DWDM systems with high spectra 1 efficiency over 1 bit / s / Hz, 丨 IEEE J. of Quantum Electron., pp · 2080-2088, Vol. 34 ·, No · 18, December, 1998.), but when the number of transmission channels increases, this architecture must follow the increased Quantity, add a spectroscope. It also uses many-to-one optical switches, which is usually very large. When the number of channels is changed, the response is also very complicated. Especially, the cost of optical switches will increase significantly with the number of available channels. This many-to-one optical switch, as far as it can be seen, should be mechanical. The switching speed is therefore slower: it may be nearly a thousand times slower than using the scanning method. In addition to the above-mentioned architecture, other known related element technologies include US Patent Nos. 5, 7 9 8, 8 5 9 and 5, which use the principle of etalon (Eta Ion) and the principle of chamfered angle, No. 8 2 5, 7 9 2; US Patent Nos. 5, 9 6 3, 6 8 6 and 6, 0 8 8, 1 4 2 using optical filters; using fiber Bragg gratings (Fiber Bragg Grating), U.S. Patent No. 6,0 5,8,31; and U.S. Patent No. 5,777,763 using gratings. [Objective and Summary of the Invention]

Page 7 480331 V. Description of the invention (5) The main purpose of the present invention is to propose a new multi-wavelength optical monitor architecture, which has a streamlined architecture, high scalability, and high processing speed. The present invention mainly uses a tunable optical filter to scan the light sources of each channel, in other words to monitor the light sources of different transmission channels, and then uses an optical filter with a fixed channel interval as a pattern mask. It is used to monitor the center wavelength of the light source, the uniformity of the transmitted light quantity, or the signal-to-noise ratio (SNR) of the optical signal. This design is different from the wavelength locking method of a laser light source with a single dfb structure. Second, it is not a technology that separates each transmission channel and then monitors it. Therefore, the present invention avoids a huge optical path. In parallel, there is no problem of insufficient expandability and high cost due to the use of optical switch technology. The invention only needs to split a small part of the light in the output light source of the multiplexer, and then relies on the adjustable optical filter. 2 Scanning action / Sequentially selecting the light source of a channel in turn = Make: "Enter the second stage of the fixed channel channel optical filter, and then process the optical signal. The next step is the architecture designed according to the present invention, Allows us to use for scanning. The optical characteristics of the modulated light / contrast wave are not limited, regardless of the a # suppression ratio (SMSR) or line width (1 丨 newidth) of the optical theory. Even, German, mode The wavelength positioning at the time of scanning must also be very accurate, and the synchronization requirements are not high, because ° is an optical filter that can be followed by a fixed channel interval to achieve the function of precise positioning ~. The production of an adjustable optical filter for scanning can speed up the scanning speed. As for the second stage of the fixed channel spacing, the optical filtering requires good and stable optical characteristics. However, it does not require Dynamically change its optical characteristics. ~

480331 V. Description of the invention (6) The detailed technical content and embodiments of the present invention will be described later in conjunction with the drawings. [Detailed description of the embodiments] The multi-wavelength light source monitor disclosed in the present invention avoids large optical paths in parallel. It only needs to divide a small part of the light source after the DWDM multiplexer, and then complete the monitoring of the multi-wavelength light source through the division of the two-stage optical filter. The first stage of the optical filter is through an adjustable The optical filter sweeps the light sources of each channel one by one; the optical filters in the second stage use the fixed channel interval optical filter as a pat ter mask to monitor the center wavelength of the light source and the amount of transmitted light. Uniformity, or the signal-to-noise ratio of transmitted light. First, please refer to "Figure 3", which is a basic system architecture diagram based on the above technical principles of the present invention. It includes: a beam splitter 20, which extracts a small part of the light source from the multi-wavelength light source For example, the optical splitter 20 is connected to the output fiber F of a high-density multi-wavelength multiplexer (DWDM), and a small part of the light sources in the output optical fiber F are branched out; a tunable optical filter 30, It is connected with the optical splitter 20, and is used to select a certain wavelength range from the multi-wavelength light source derived from the optical splitter 20, that is, a light source of a transmission channel;

A fixed channel interval optical filter 40 has a fixed channel interval for taking out a light source required for monitoring from a light source selected by the adjustable optical filter 30; a light detection unit 50 and a fixed Channel-spaced optical filter 40 is connected to convert the intensity of the light source required for monitoring into the corresponding electrical signal.

480331 V. Description of the invention (7) and outputting this electric signal; An operation control and signal processor 60 for processing the electric signal from the light detection unit 50 into data representing the optical characteristics of the light source for monitoring The basis of a multi-wavelength light source; and a wavelength controller 70 controlled by the operation control and signal processor 60 to sequentially adjust the filtering wavelength of the tunable optical filter 30 in order to scan one by one ( swap) light sources of different wavelengths in a multi-wavelength light source. In the foregoing basic system architecture, the optical path design of the tunable optical filter 30 and the fixed channel-spaced optical filter 40 can also be implemented through the following embodiments. The first example of the optical path is shown in "Figure 4"; a small portion of a multi-wavelength light source derived from the splitter 20 is first used to select a light source of a certain wavelength through a tunable optical filter 30. Then, the selected light source is divided into two, and one of them is guided through a fixed channel-spaced optical filter 40, and then guided to a first light detector 5 in the light detection unit 50. 0 1, which is converted into an electric signal corresponding to the intensity of the light source; the other is used as a reference light source and is directly guided to a second light detector 5 0 2 and converted into an intensity corresponding to the light source Telecommunications signal. And the electric signals from the first photodetector 501 and the second photodetector 502 are compared with the operation control and the signal processor 60, respectively, to obtain data representing the optical characteristics of the light source. Then use the operation control and signal processor 60 to adjust the filtering wavelength of the tunable optical filter 30, so as to continue to select the next wavelength light source for monitoring. Especially when the power of the light source is unstable, the values measured at different time points will be different.

480331 V. Description of Invention (8) Means have become the necessary solution. The second example of the optical path is shown in "Figure 5"; a small portion of the multi-wavelength light source derived from the splitter 20 is first used to select a light source of a certain wavelength through a tunable optical filter 30. Then, the selected light source is divided into two. Both light sources pass through an optical filter 40a with a fixed channel spacing of two output ports 401a and 401b, and the attenuation of the light intensity changes with the light wavelength. The two light sources have different period changes. These two periods are generated to obtain the characteristics of the light source through a pre-designed tunable optical filter 30. Two photodetectors 5 0 1, 5 0 2 are used respectively. Detect the light intensities of two light sources, convert them into electric signals corresponding to the intensities of the light sources, and then process the electric signals output by the two light detectors 50 1 and 50 2 to know the required Optical characteristics. The second example of the optical path is shown in "Figure 6"; a small portion of a multi-wavelength light source derived from the splitter 20 is first used to select a light source of a certain wavelength through a tunable optical filter 30, Then, the selected light source is divided into two, and the two light sources pass through two fixed channel-spaced optical filters 4 0 b and 4 0 c, respectively. The attenuation of the light intensity changes with the wavelength of the light, but the period of the two light sources The changes are different. These two cycles are also generated to learn the characteristics of the light source through a pre-designed adjustable optical filter 30. Two photodetectors 5 0 1 and 50 2 are used to detect two channels. The light intensity of the light source is converted into 0 corresponding to the intensity of the light source, and then the electrical signals output by the two photodetectors 5 0 1, 5 0 2 are processed to obtain the required optical characteristics. . The so-called tunable optical filter 30 in the above three embodiments can be

V. Explanation of the invention (9) The following example uses the following several optical devices. The first example is to use a "two" which is: (Acusto-Optic Turnabie ^ ° cycle filter state). The optical filter is 3 0. To adjust its driving sore A 〇TF), as an adjustable RF frequency enough to filter through a certain wavelength of light in turn, so that A0TF can be a wavelength locker (as a fixed channel, and then enter etalon as the core measurement two The photodetector 501, 502's light transmission filter 4), the last amount of offset can be used as the channel (= f 'can be converted into wavelength data or feedback control basis. Then π / wavelength The light source) monitors its wavelength range aligned to the next channel, and the frequency of the controller 70 makes it possible to monitor all channels step by step (:: the steps described. In this way, we can dynamically change what we want to monitor The four-pass optical source. I < the door found that in our system, the number of channels and the center; the light source is not affected by the system. The second example is using an optical fiber to: contain. Optical filter (Flber Fabry-Perot / ... Powell-type adjustable FFP-TP) for scanning action, Una e filter: (PieZQelec: tle. PZT) q 22 to 3 through the use of piezoelectric thickness , It adjusts the medium of FFP-TP by changing the optical path difference; f technique. In the third example, we use the purpose of 2: 1 "to filter the wavelength. I :: tune = Edit 3. ^ Is used as the scanning wavelength to perform the scanning action, and the change of its central wavelength is changed to ^ = the tension or temperature imposed on it. If it is changed to the optical filter 40 with a fixed channel interval, it can be a few below V This kind of optics is realized, it is as follows:

480331 V. Description of the Invention (ίο) In the first example, we can use the Mach-Zehnder interferometer to design the required fixed channel interval optical filter 40. With the use of the aforementioned ATF, we can monitor the The amount of transmitted light can be further monitored for its signal-to-noise ratio (SNR) or used to monitor the wavelength offset. In the first example, we can use a forged film filter (group) with multi-wavelength reflection to design the required fixed channel interval optical filter 40. Similarly, in conjunction with the aforementioned A0TF, we can monitor the amount of transmitted light in each channel. It can be further monitored for its signal-to-noise ratio (SNR) or used to monitor wavelength offset. In the second example, we can use a multi-wavelength reflecting fiber grating (FBG) (group) to design the required fixed-channel-spaced optical filter4. Similarly, in conjunction with the aforementioned AOTF, we can monitor the transmitted light amount of each channel It can further monitor its signal-to-noise ratio (SNR), or to monitor the wavelength offset. [Effect of the invention] According to the technical content of the present invention, it can have the following effects: 1. Comparison of optical characteristics The optical characteristics of scanning optical filters are not high. In this way, the production of the optical filter for scanning can be simplified and the speed of scanning can be accelerated. As for the optical filter with a fixed channel interval in the second stage, although it needs good and stable optical characteristics, it does not need to dynamically change its optical characteristics. . Traditionally, only AOTF-based technology is used. The final scanning spectrum is the input laser source spectrum and the “convolution” of the AOTF transmission spectrum. So the line width of A0TF is too wide, it will definitely be inferior

Page 13 480331 V. Explanation of the invention (π) The wavelength resolution of the system (half of the typical half-height line width of A0TF is about 0.5n ', but for 100GHz DWDM communication systems, the center wavelength interval is 0.8nπ〇; especially It is unavoidable that the light wave's line width after signal modulation will be increased. Especially today, the communication demand is increasing day by day, and it is becoming more and more highly spectral efflciency, that is, the channel interval is narrow, but the required transmission speed However, it is even faster, and the line width becomes wider. In this way, the result of the "swing integral" of the two spectra will make the measured line width more extended, so that adjacent channels will seriously interfere with each other, The monitoring system may deteriorate to the point where it cannot be used. Similarly, the drift of aot wavelength to temperature will also complicate its synchronous action, and it may also require frequent two-calibration work, which increases the complexity of the system. (Because of the use of optical components, light sources, etc.); and under the condition that the side mode suppression ratio is not good, the crosstalk (cr0sstaU) of the side channel is combined into one: Dynamic range. Further, for any optical frame that adopts a single scanning method, it is difficult to avoid the convolution. However, the tunable optical filter in the present invention is used to select a certain wavelength ^ Asian and African use the "round-robin integral" method. # 出 光光 ：: The line width should not be too wide, and it will not lead to the introduction of neighboring cats. This: the side-mode depression ratio of the foot may also pass through the :: = road interval. The light filter 'wave filter is improved. Of course, the first one can be used; ^ The lack of the first filter in the spectrum will eventually affect the under-spectrum. Regardless, through the framework of the present invention, it can be: == on the spectrum The lack of A0TF is more convenient for the commonly used supplement. Feiyou Bowei, in 480331 V. Invention Description (12) For the traditional architecture using multiple beam splitters, its optical characteristics may be Superior to the present invention: the reason is that the way of selecting a wavelength is to use a beam splitter and an optical switch. The above two elements do not need to control the wavelength conversion, and the specifications are easier to achieve: the important optical characteristics that the beam splitter needs to maintain Is to maintain The light ratio is fixed, and the amount of light that passes through it is controlled, which varies with the operating wavelength and temperature. The important optical characteristics of the optical switcher are the isolation rate and the switching time. However, because each channel passes through a different optical splitter, its The calibration of cavities (ca 1 ibrati ο η) such as temperature changes and changes in the passing central wavelength is bound to become more complicated. And the complexity gradually deteriorates with the increase of the number of channels. Second, the execution speed is more traditional and simple The A0TF architecture is most likely to adopt a linear wavelength scanning method to obtain a complete spectrum; while the present invention can use a stepped wavelength scanning method to provide a longer detection time only for the required center wavelength (two scanning methods) Comparison, as shown in "Figure 7"), if the scanning time of each point in the spectrum is fixed, stepwise scanning is not necessary, so it will save a lot of speed. Especially in the case of large optical noise, it is more significant when scanning must take a long time average (t i m e a ν e r a g e). If the structure of the optical splitter is used, an optical switch is needed in the system. Because of its condition, similar to the case of spatial multiplexing, almost all mechanical switches with movable parts must be used. The response speed of the system is limited by the weight of the moving parts in the optical switch (the response speed is directly proportional to the weight of the weight). In most cases, it is about a few ms.

Page 15 5. Description of the invention (13) On the order of magnitude, compared to acousto-optic components (such as A0TF) 'is about -1000 times worse than the car parent. Similarly, when the mechanical light],:, and * phase, the time of each switching also becomes longer; phase === mesh

Software, but there are no such disadvantages. Comparison of the complexity and expansibility of the nine-type 7L system. Similarly, using only A () TF, such as the linear method, the reading of the wavelength depends entirely on the relationship between the frequency of the A0TF and the field frequency. It is necessary to introduce precision warm production first ;;, to drive the light source of the electric test (such as the absorption spectrum of a gas lamp with a gaseous element, and when the optical communication; =: to find; and to r; = frequency; this is relatively adjustable The wavelength of the element is not equal to 5 weeks of integration and replacement, in comparison, the cost is lower. Even if the m-structure is introduced, when the number of optical paths increases, it will increase a lot ... if there is no reservation === the number of paths also You have to wait for the switcher to change to a larger switch. Regardless of the structure, the larger and larger the switch complexity of the switch n is, the structure of the present invention, if the number of optical paths is increased first :: time = time, time is two, and What needs to be adjusted is only the method of AOTF sweeping: the interval of I channels is not changed at the same time. The condition is shown in the previous paragraph; the square is equal to the range. If the interval is also using a mechanical optical switch, for example, because the moon is not used, Time through this monitoring, with the light

Page 16 480331 V. Description of the invention (14) The increase in the total number of routes should be less obvious. 480331 Brief Description of Drawings Figure 1 is a system architecture diagram of the conventional optical technology using a single A0TF monitoring light source. FIG. 2 is a system architecture diagram of a conventional technique for monitoring optical characteristics of a light source using a spectroscope and an optical switch. Figure 3 is a basic system architecture diagram of the present invention. Fig. 4 is a partial structural diagram of the present invention, showing a first optical path embodiment of an adjustable optical filter and an optical filter with a fixed channel interval. Fig. 5 is a partial structural diagram of the present invention, showing a second embodiment of an optical path of an adjustable optical filter and an optical filter with a fixed channel interval. Fig. 6 is a partial structural diagram of the present invention, showing a third optical path embodiment of an adjustable optical filter and an optical filter with a fixed channel interval. Fig. 7 is a comparison chart between the present invention and the traditional scanning center wavelength using only A0TF. [Illustration of Symbols of Drawings] Known Techniques 10 ........ Optical Splitter 11 ........ Adjustable Optical Filter 12 ........ Light Detector

13 ........ operation control and signal processor 14 ........ wavelength controller 15 ........ multi-wavelength multiplexer 16 ....... .Optical Switcher 17 ........ Channel Controller

480331

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Claims (1)

480331 6. Scope of patent application 1. A multi-wavelength light monitor for monitoring the optical characteristics of a multi-wavelength light source in a fiber-optic communication system, which includes: a beam splitter that extracts a small portion from a multi-wavelength light source A tunable optical filter connected to the spectroscope to select a light source of a certain wavelength range from the multi-wavelength light source derived from the spectroscope; a fixed channel interval optical filter, It has a fixed channel interval for taking out the light source required for monitoring from a selected light source selected by the adjustable optical filter; a light detection unit connected to the fixed channel interval optical filter for connecting the monitoring station The required light source intensity is converted into the corresponding electric signal 'and the electric signal is output. An operation control and signal processor is used to process the electric signal from the light detection unit into data representing the optical characteristics of the multi-wavelength light source as the data Basis for monitoring multi-wavelength light sources; and a wavelength controller controlled by the operation control and signal processor to sequentially adjust the tunable optical filter Pass filter's wavelength to individually scan (s w a p) of the respective light sources of different wavelengths of the multiwavelength light source. 2. The multi-wavelength optical monitor as described in item 1 of the scope of the patent application, wherein the beam splitter is connected to an output port of a high-density wavelength multiplexer (DWDM), and is used to divide a small part of the light sources therein. Leads out. 3. The multi-wavelength optical monitor as described in item 1 of the scope of patent application, wherein the Page 20 480331 6. The patent application scope of the tunable optical filter selected a certain wavelength of the light source is divided into two, one of which is guided through the fixed channel interval of the optical filter, and then directed to the device The first signal of the light detection unit of the light detection unit which is used as a reference light source to detect the electrical signal which should be converted to the photodetector should be directly guided to the second of the light detection unit. The light detector converts it into an electrical signal corresponding to the intensity of the light source. For example, the third tunable optical filter in the scope of patent application adjusts the light of a specific wavelength of its driving circuit to the output power of an etalon as a nuclear photodetector. One or two filters selected. The two light sources have two output ports. The intensity reduction is a multi-wavelength light monitor described in terms of the wavelength of light. Among them is an acousto-optic tunable filter (A0TF). Through the RF frequency, the A0TF can be filtered in turn, and the wavelength locker of the optical filter center of the fixed channel interval measures the two pressure differences to obtain the periodic variation of the wavelength offset of the light source. Unsteady changes between channels. One of the first photodetector and the other corresponding to the intensity of the light source, as specified in the patent application scope of the first tunable optical filter, is selected. The periodicity of the two light sources does not change. Telegraph. The multi-wavelength light monitor described in the above item, wherein the light source of the wavelength is divided into one and the same, and they are all passed through an optical filter with a separation, so that the light is not converted by the light detector of the light detection unit into Phase wavelength light monitor, in which the light source of this wavelength is divided into two Page 21 480331 6. The scope of the patent application The optical filter with a fixed channel spacing changes its light intensity attenuation with the wavelength of the light, and then uses a first light detector and a second light in the light detection unit, respectively. The detector converts it into an electrical signal corresponding to the intensity of the light source. 7. The multi-wavelength optical monitor described in item 1 of the scope of the patent application, wherein the tunable optical filter is a fiber Fabry-Perot tunable filter (Fiber Fabry-Perot tunable filter: FFP-TP) uses piezoelectric (PZT) modulation technology to adjust the dielectric thickness of the FFP-TP, and then adjusts the filtered wavelength by changing the optical path difference. 8. The multi-wavelength light monitor as described in item 1 of the scope of the patent application, wherein the tunable optical filter is a fiber grating (Fiber G rating), which is made by changing the center wavelength of the reflection spectrum of the fiber grating. Scanning action. 9. The multi-wavelength light monitor as described in item 8 of the scope of the patent application, wherein the means for changing the center wavelength of the fiber grating is accomplished by changing the tension applied to the fiber thumb. 10. The multi-wavelength optical monitor according to item 8 of the scope of the patent application, wherein the means for changing the center wavelength of the fiber grating is accomplished by changing the temperature applied to the fiber grating. 1 1. The multi-wavelength optical monitor according to item 1 of the scope of patent application, wherein the optical filter with a fixed channel interval is a M a c h-Z e h n d e r interferometer. 1 2. The multi-wavelength optical monitor as described in item 1 of the scope of patent application, wherein Page 22 480331 6. Scope of patent application The optical filter with fixed channel spacing is a coated filter (group) with multiple wavelength reflection. 1 3. The multi-wavelength optical monitor according to item 1 of the scope of the patent application, wherein the optical filter with a fixed channel spacing is an optical fiber grating (FBG) (group) with multi-wavelength reflection.