Introduction

In recent years, with the widespread deployment of 5G, global traffic has grown rapidly and bandwidth has been rapidly improved. At the same time, the outbreak of the new coronary pneumonia epidemic has prompted a sharp increase in demand for data centers and fiber-to-the-home, bringing considerable demand to the optical communications industry. The market demand for optical modules, wavelength division devices, splitters and connectors continues to grow, and fixed networks and access networks have also ushered in a new construction cycle. The optical module is a key component of the optical communication equipment, and the optical communication device is the main component of the optical module, and its performance determines the upgrade and update of the optical communication network, and the laser is the most important electro-optical conversion device in the optical module. With the rapid development and breakthrough of semiconductor laser technology, semiconductor lasers have a series of advantages such as small size, light weight, high electro-optic conversion efficiency, strong stability, high reliability and long life. At present, the quality, wavelength range and output power of semiconductor laser products are rapidly improving, and the variety of products is becoming more and more abundant. The application of semiconductor lasers has covered the entire field of optoelectronics and has become one of the core technologies of optoelectronic science today. Therefore, semiconductor lasers are considered to be one of the most promising areas in the optoelectronic industry.

There are several types of semiconductor lasers, including vertical-cavity surface-emitting lasers (VCSEL), Fabry-Perot lasers (FP),distributed feedback laser(DFB) and electro-absorption modulated laser (EML), etc. These lasers are different in terms of performance and cost, so when selecting an optical module, different chip solutions need to be selected according to specific specifications.In the semiconductor laser family,DFB laserBecause of its excellent spectral characteristics and modulation characteristics, it has become one of the most important and widely used light sources in communication systems. The concept and theory of DFB laser were first proposed by H.Kogelnik and C.V.Shank of bell laboratory in 1971-1972. the earliestsemiconductor DFB laserappeared in 1973. After nearly 50 years of development, DFB lasers have been widely used in optical communications, sensing, mapping and other fields. In the field of optical fiber communication, with its excellent single-mode operating characteristics, DFB lasers have become wavelength division multiplexing (WDM) Important light source of the system. With the development of technology and demand, the application fields of DFB lasers have become more and more diversified in recent years.

This paper mainly analyzes the global and Chinese DFB laser invention patents from the annual application trend, applicants, technology distribution and other dimensions, and analyzes and refines the layout characteristics of the patent data after screening and cleaning, which is convenient.Domestic DFB laserRelevant institutions understand the current situation of global and domestic patent layout in this field, assist them to find out the potential patent risks, clarify the direction of technology development, formulate more practical patent development strategies and risk response plans, and comprehensively enhance the comprehensive intellectual property capabilities of China's DFB laser industry.

1. DFB laser global patent layout

As of December 31, 2021, the published data sources are based on the patent libraries of the seven organizations (the seven organizations usually refer to China, Japan, the United States, the United Kingdom, France, Germany, Switzerland, the European Patent Office, and the International Intellectual Property Organization).distributed feedback laserA total of 9,832 invention patents were applied for, of which 5,526 were merged into the same family.

As shown in Figure 1, distributed feedback technology appeared earlier. DFB laser patents first appeared in 1975, but the applications were scattered before 1981. Subsequently, DFB technology was paid attention to and was applied to lasers, which led to a rapid increase in the number of patent applications. Although the number of patent applications fell from 2003, the total application trend was still increasing, indicating that research and development activities were still very active. Since patents have an 18-month publication period, the number of patent applications that can be retrieved in 2020-2021 is not representative of the true application situation. However, with the rapid development of laser technology and the popularization of 5G technology, the number of patent applications for DFB lasers will continue to increase compared with the past.

Figure 1 Global annual patent application trends for DFB lasers in the past 20 years (unit: item)

FigureAs shown in 2, due to the early emergence of DFB technology, 3,371 DFB laser patents have expired worldwide, accounting for 62% of the total number of patents in the world, with a large proportion of failures. By the end of 2021, 23% of the world's patents are still valid, I .e. have been granted, and the proportion of valid patents to total patent applications is small. A further 13 per cent of the patents are under examination, and it is not clear whether these patent applications can be patented. According to statistics from the Intellectual Property and Innovation Development Center of the China Academy of Information and Communications Technology, more than 50% of these invalid patents are invalid due to the withdrawal of patent applications, 25% are invalid due to failure to pay annual patent fees and other reasons, 15% are invalid due to rejection, and 10% are invalid due to expiration of the term.

Figure 2 DFB laser global patent legal status statistics

As can be seen from the geographical distribution of DFB's global patents (see Figure 3), Japan, China and the United States are the key countries, with 30%, 27% and 19% of invention patents respectively. The analysis of patent data shows that the patent development trend of Japan, China and the United States is not the same, of which Japan isDFB laserThe largest target country for patent layout is mainly due to the large number of Japanese optoelectronic chip companies, strong technological innovation, and focus on local market development. China is the second largest target country for the patent layout of DFB lasers. On the one hand, it lies in the active layout of Chinese local enterprises/institutions, and on the other hand, the huge potential of the Chinese market has attracted the attention of all forces from all over the world. The United States is the third largest important market for DFB lasers after China, which is closely related to the intensive technology research and development activities and the active consumer market in the United States.

Figure 3 DFB laser global patent geographical distribution

From the distribution of DFB laser global patent technology source country can be seen (see Figure 4), the patent technology source country to a certain extent reflects the overall technical research and development strength and technological innovation capability of each country in DFB laser. Through the analysis of patent data, it can be seen that Japan, the United States and China are the main source countries of DFB laser patent technology, indicating that the above three countries are the most active regions in the field of DFB laser chip innovation. Japan is by far the largest source of DFB laser patent technology, 33% of the patented technology by Japanese applicants. As one of the most technologically developed countries in the world, the United States has a number of chip, device, and equipment company giants. These companies have applied for 29% of the world's DFB laser invention patents. As the world's third largest source of DFB laser patent technology, China has actively contributed 1,716 invention patents from different types of enterprises, scientific research institutions and universities, accounting for 23% of the total number of global patents.

Figure 4 Distribution of global patent technology source countries of DFB laser

in the globalDFB laserIn the patent technology distribution (see Figure 5), the global DFB laser patent technology research and development hot spots mainly focus on laser modules, generators, detectors, interferometers, quantum cascades, compounds, multiplexers, etc. Of these, 23.5 per cent are concentrated in the International Patent Classification (IPC) classification number H01S5/00, I .e. methods or devices for semiconductor lasers or their components. 23.2% is concentrated in the IPC classification number H01S5/12, that is, the resonant cavity with periodic structure. 6.5% is concentrated in IPC classification number H01S5/042, the electrically excited structure. 4.6% is concentrated in IPC classification number H01S5/06, that is, the device that controls the output parameters of the laser, such as controlling the activation medium.

Figure 5 Global DFB laser patent technology distribution (unit: item)

2. DFB laser Chinese patent layout

As shown in Figure 6, as of December 2021, the number of Chinese patent applications for DFB lasers reached 2,129, with a total of 1,917 merged families, showing an increasing trend year by year. Different from the international application trend, the Chinese patent for DFB laser appeared late, and the first application began in 1995. But then the number of patents grew significantly, the proportion of patents is getting higher and higher, it can be seen that the Chinese market by the attention of patent applicants, and domestic scientific research institutions and related enterprises as a whole in the rapid catch-up stage of technology, innovation activities are active, but also make the number of DFB laser patent applications is relatively large.

Figure 6 Global/Chinese annual patent application trends for DFB lasers in the past 20 years (unit: item)

35% of DFB laser patent applications in China are in a valid state, and the proportion of valid patents is high. Only 30% of the patents in the trial state, and it is not clear whether these patent applications can be patented. However, 35% of the patents are in a state of failure. Compared with the international patent failure, the layout of domestic patents is more scientific and reasonable.

Chinese local applicants are the main source of patent technology for DFB laser patents in China. U.S. enterprises have only distributed 8% of Chinese DFB laser patents in China, Japanese enterprises have distributed 4% of patents in China, and foreign patentees have not carried out too many international patent layouts for DFB lasers.

In the distribution of Chinese patent technology for DFB lasers (see Figure 7), 24.3 of the Chinese DFB laser invention patents are concentrated in IPC classification number H01S5/12, which is a resonant cavity with a periodic structure. 16.5 percent is concentrated in G01N21/39, which utilizes tunable lasers. 9.4 percent is concentrated in H01S3/067, the fiber laser. 8.1% is concentrated in H01S5/22, that is, with a ridge or stripe structure. 7.7 are concentrated in H01S5/343, that is, materials with AⅢB Ⅴ compounds. The analysis of patent data shows that the technical hotspots of China's DFB laser patents are mainly distributed in detectors, optical modules,wavelength division multiplexinggenerator,Light sourceDiode,Isolator,CirclipLimiting layer, etc.

Fig. 7 Patent Technology Distribution of DFB Laser in China (Unit: Item)

Analysis of important patents of 3. DFB laser

Due to the long development time of distributed feedback technology and the existence of many technical routes, global DFB laser patents are frequently cited among enterprises. For example, the invention patent US20040151222A1 applied by Fujitsu Co., Ltd. on December 30, 2003 mainly protects the structure of a tunable dual-waveguide DFB laser, simplifies the management of tunable light sources, and can dynamically change the routing destination according to wavelength. This patent has been cited more than 192 times so far. The main cited company is "Soraa Laser Diode,Inc" (acquired by Kyocera Group in 2020). Most of the cited patents are located in the United States. The company mainly develops, manufactures and sells high-efficiency and high-brightness innovative products based on laser technology, which are suitable for mobile equipment, special lighting, consumer and industrial applications. The high-frequency citation by a company fully shows that this patent is very important to Kyocera Group, and it is only on this patent that a perfect patent layout has been set up to increase the intensity of protection. However, due to the failure to pay the patent maintenance fee, its rights were terminated on April 23, 2018. Considering that the patent has been cited so frequently and the importance of technology, it is suggested that the relevant institutions in China can study the patent scheme in depth to confirm whether it has the value of reference or improvement and development.

DFB laserThere are also cases in which patents are disclosed as standard patents. For example, the patent application was filed on May 18, 2004. Currently, US20040258125A and family patents US49695604, US49593704, JP2003550326, CA2468762, Fraunhofer and Gesellschaft held by AU2002363828 EP1449285A2 zur Forderung der Angewandten Forschung eV institutions are disclosed as 5G, LTE and WCDMA standard patents in ETSI, with version numbers of TS 123 271 v15.1.0, TS 23.271(15.1.0) and TS 23.271(6.4.0). The patent solution mainly protects a device for generating optical microwaves in the frequency range of 0.5 GHz to terahertz through a multi-segment semiconductor laser, and its microwave source realizes feedback intensity that cannot be achieved by a purely passive external cavity. At the same time, the patentee has also laid out the same family of this standard patent in the United States, Japan, Germany and other major countries, which fully shows the importance the patentee attaches to this patent scheme. It is suggested that the relevant institutions in China should pay close attention to whether the standard patent has joined the patent pool to organize the patent licensing fees, assess the market risk as soon as possible and avoid it in advance.

4. closing remarks

After years of efforts, some universities, research institutions and enterprises in China have made certain technical reserves and industrial accumulation in the field of DFB lasers. With the continuous advancement of 5G construction in stages and the vigorous development of 5G carrying optical module industry, a benign ecology of China's DFB laser industry will be comprehensively constructed by integrating intellectual property resources in all aspects of China's DFB laser industry, actively transforming high-quality DFB laser patents from universities and research institutes to enterprises for use, and encouraging China's DFB laser research institutes and enterprises to deeply participate in international standardization work, to enhance the comprehensive strength of China's DFB laser industry in the international market.

Source: Laser Industry Watch