1. The definition of  Free space WDM 

Free space WDM is an optical communication technology. It means that in the optical communication system, optical signals of different wavelengths are processed in a free space environment without relying on optical fiber as the transmission medium. Methods of reuse and demultiplexing. In free-space WDM, optical components (such as lenses, mirrors, diffraction gratings, etc.) are used to manipulate light of different wavelengths to achieve separation, combination, and transmission of optical signals. This technology can simultaneously transmit multiple optical signals of different wavelengths in the same physical channel, thereby greatly improving the transmission capacity and efficiency of the communication system.

2. Free space technology

CCWDM is a compact version of CWDM. It is based on the wavelength division multiplexing technology of TFF (thin film filter), but uses free space technology to realize the cascade of optical signals. Specifically, CCWDM utilizes free space technology in the following ways :

(1) Optical signal focusing: CCWDM uses the input lens to focus the multi-wavelength optical signal on the input fiber onto the first filter. This step is the preliminary processing of optical signals in free space.

(2) Optical signal separation: Optical signals of different wavelengths will be separated when passing through the filter. For example, the optical signal with wavelength λ1 will pass through the first filter and be coupled into the first output fiber through the output lens, while the remaining optical signals will be reflected to the next filter for further separation.

(3) Parallel beam cascade: The adjacent channels of CCWDM use parallel beams to cascade in free space, instead of using optical fibers to cascade like traditional CWDM. This approach greatly reduces package size and insertion loss.

(4) Zigzag route coupling: The coupling between wavelength channels is realized in the form of collimated light rays taking a zigzag route, which further improves the transmission efficiency of optical signals.

3. Hirundo will  attend OGC and CIOE with CCWDM & CDWDM

From September 11th to 13th, Hirundo will attend the 25th China International Optoelectronics Expo with our mini WDM series - CCWDM & CDWDM. At the same time, in order to promote cooperation with more universities and scientific research institutions, Hirudno sponsored the 9th  OGC, hoping to provide a communication platform with international scholars, researchers, and practitioners in the field of optoelectronics to discuss the future of the optoelectronics industry. New developments, new ideas and new technologies.

4. Comparison of the advantages and disadvantages of free space products and ordinary CWDM

2. Free space WDM products typically have the following characteristics
 

1) Wavelength selectivity: Accurately select and separate optical signals of different wavelengths. Each wavelength can carry specific services or data. For example, different wavelengths can be used to transmit different types of communication services, such as voice, data, video, etc., allowing multiple services to be transmitted simultaneously without interfering with each other.

2) Low insertion loss: When the optical signal passes through the WDM device, the insertion loss is low, which ensures that the power attenuation of the optical signal during transmission is small, which is conducive to long-distance transmission. For example, the insertion loss of some high-quality WDM products can be controlled at a low level (such as within a few dB), allowing the optical signal to maintain sufficient strength after being transmitted over long distances.

High isolation: The isolation between different wavelengths is high, which can effectively prevent crosstalk between optical signals of different wavelengths and ensure that optical signals of each wavelength can be transmitted and received independently and Accurately.

Small size: Free space WDM products use parallel optical path connection levels, which are different from the optical fiber connection level of CWDM, which greatly saves space. The package size of CCWDM module accounts for about 1/4 of CWDM.

4. Applications of free space products

1. wireless optical communications

Wireless optical communication is a communication method that uses light waves to directly transmit information in free space. Free-space WDM technology can be applied in this system to achieve high-speed and large-capacity data transmission by multiplexing multiple optical signals of different wavelengths on the same free-space path. For example: FSO systems are usually used in short-distance, high-speed communication scenarios, such as interconnection between urban buildings and fast data transmission between data centers. Free-space WDM technology can further improve the transmission capacity and efficiency of these systems.

2. Integrated WDM system

Compared with open WDM systems, integrated WDM systems are characterized by specific requirements for the wavelength of multiplexed terminal optical signals. In an integrated WDM system, the wavelength of the optical signal sent by the multiplexing terminal needs to comply with the specifications of the DWDM (Dense Wavelength Division Multiplexing) system. This means that different multiplexing terminal equipment needs to send different wavelengths that comply with the recommendations of ITU-T (International Telecommunications Union Telecommunications Standards Bureau) in order to occupy different channels when accessing the combiner to complete the combining operation.