Single-mode fiber couplers are the most common optical fiber couplers used for splitting and combining optical signals. By controlling the length and diameter of the fusion zone where energy transfer occurs between two optical fibers, we can manufacture a coupler with an arbitrary coupling ratio.
With its wavelength dependency on the coupling ratio, single-mode fiber couplers are suitable for a system using a narrowband light source such as LD. For a system using a wideband light source such as SLD or ASE, wideband couplers that suppress the wavelength dependency on the coupling ratio to a small extent are recommended to prevent deterioration of the spectral characteristics of the light source.

Wideband couplers, or Wavelength Flatted Couplers (WFCs), are characterized by their small wavelength dependency on the coupling ratio. Our WFCs have extremely high wavelength flatness and are widely used in Optical Coherence Tomography (OCT) applications.
In selecting a wideband coupler, you should not make the operating wavelength wider than necessary. The wider the operating wavelength, the lower the wavelength flatness, which may result in greater wavelength dependency in the actual wavelength range that is used. We recommend you check the specifications of the light source that you are using before selecting the optimal coupler. If you have any problems in selecting a coupler, please feel free to contact us. We are happy to help you select the optimal coupler.

Standard product example

The following chart shows the coupler performance at 1050nm with a coupling ratio of 50:50. The flatness of the coupling ratio is maintained from the center to the wideband wavelengths.
We can propose and select a coupling ratio tolerance rank according to your application.

Custom-made product example

You can specify the center wavelength, wavelength band, coupling ratio, and grade.

Rank	Tolerance
regular	±5%
special	±3.5%
premium	±2%

Wavelength Division Multiplexing (WDM) couplers are used to multiplex and demultiplex optical signals of different wavelengths. In communications applications, WDM couplers are widely used for multiplexing/demultiplexing of signal light (signal) and exciting light (pump) in optical amplifiers.
In addition to optical amplifier applications, we have commercialized dual- and triple-wavelength-band WDM couplers covering visible (VIS) band used for fluorescence analysis of laser microscopes, and infrared (IR) band used for gas measurement, ahead of competitors.
Due to the difficulty of visually identifying the irradiation point of the light source, measuring instruments and laser machines that use near-infrared (NIR) wavelengths may use a red or green visible (VIS) laser as a guide light. We also offer dual-wavelength-band WDM couplers covering near-infrared (NIR) and visible (VIS) wavelengths to multiplex a signal light and guide light.
In general, it is difficult to manufacturer a WDM coupler when you use two close wavelengths. The difficulty of manufacturing depends on the wavelength band and the wavelength interval between the two wavelengths to be multiplexed. We are ready to respond to your inquiries for custom-made specifications.

Standard product example

The following chart shows the performance of a WDM coupler at 1050 nm/550 nm and 1300 nm/660 nm.
The coupler shows good performance over a wide wavelength range, showing its versatility.