Semiconductor laser diode module, why is the coupling efficiency of single-mode fiber lower than that of multi-mode fiber?

Semiconductor laser diode module, why is the coupling efficiency of single-mode fiber lower than that of multi-mode fiber?

Aug 18, 2020

With the development of technology and the increasing improvement of optical fiber processing technology and manufacturing technology, the transmission loss in optical fiber communication and optical fiber sensing has been reduced to the limit. The coupling efficiency of the laser light source and the optical fiber is becoming more and more prominent.


In fiber optic sensing, the coupling of multimode fiber and light source is much easier than single-mode fiber, but because single-mode fiber has a higher lateral resolution, in some special sensing test occasions, single-mode must be used. optical fiber. Therefore, improving and enhancing the coupling efficiency of semiconductor laser light source and single-mode fiber has become the focus of domestic and foreign laser industry research.

 photobank (30)

Since the core diameter of a single-mode fiber is only one-tenth of that of a multi-mode fiber, that is, about 5 to 10 μm, a simple sleeve coupling cannot achieve higher coupling efficiency. To reduce the optical coupling loss between SLD-SMF, the mode field radius (light spot size) of the laser should be matched with the mode field radius of the fiber, that is to say, the elliptical mode field of the laser is converted into the circular shape of the fiber. Mode field, this can be achieved by using a lens between SLD-SMF.

 Fiber Coupled Laser(17)

Elite Optoelectronics can provide single-mode fiber-coupled lasers with wavelengths from 405nm to 980nm, with an average power of 10-80mW. We can not only achieve single-wavelength output, but also 2-wavelength or 3-wavelength RGB combined beam output. The average coupling efficiency can reach 60-70%. For different applications, we can provide standard size, Mini size, and customized size. Especially for 405nm, under the premise of ensuring high coupling efficiency, we can provide about 300mw of power. Because 405nm is a special wavelength, 405nm single-mode fiber needs special treatment and needs to be coated with a special protective film. If these treatments are not done, the optical fiber will be burned out, the power will be greatly reduced, and the service life of the product will not exceed half a year.

 Fiber Coupled RGB(3)

Elite offers superior performance, reliability, and stability Bios series SMF laser, special design for DNA detection instrument, flow cytometer, and biological detection instrument.

 Fiber Coupled Laser(8)

If you need more information about the laser products, pls contact freely.