Mode Controller

Creating Defined Excitation Conditions

Mode Controller for the Creation of Encircled Flux Conditions
Mode controllers are necessary to reproducibly measure attenuation losses and the bandwidth of multi-mode optical fibers. This is the only way to ensure a standard measurement setup with encircled flux conditions according to IEC 61280-4-1, which requires the creation of a defined mode structure in the fiber.

85%/85% Modal Launch Condition – Aerospace
Other excitation conditions (e.g., in aerospace applications), such as the “85%/85% modal launch condition,” are important. To be able to create these excitation conditions, the measuring equipment (light sources) has to be designed accordingly or – as is more often the case – a module used to create these excitation conditions must be inserted.

Arden Photonics’ modules meet all of the above requirements.

Measuring Device
The MPX measuring device is available for the inspection of correct modes.

Encircled Flux – Background Information

Depending on the measurement method, there are significant deviations in the attenuation measurement of multi-mode fibers.

Multi-mode (MM) fibers have a larger core diameter than single-mode fibers; therefore, the attenuation measurement is problematic: When light (e.g., from a laser (VCSEL)), is coupled into this fiber, the diameter of the beam is often smaller than that of the fiber core. This allows attenuation measurements to produce results that are too low (underfill). Vice versa, the attenuation values measured are often too high when the light enters outside the fiber core (e.g., the light of an LED source (overfill)).

To reduce these deviations in attenuation to a certain percentage, the IEC 61280-4-1 norm provides a regulatory standard. With the second edition, the term encircled flux (EF) was introduced as a parameter to define the light power distribution in the optical fiber core.

To meet the encircled flux condition, a mode conditioner (mode controller) can be inserted between the light source and the reference connector.

ModCon Compact Mode Controller

The ModCon mode controller is optimized for the wavelengths 850 nm and 1300 nm and can thus be used in combination with LED or VCSEL light sources. This component is easily connected to the light source.

ModCon Aerospace Controller – For Aerospace Applications

To achieve the 85%/85% coupling conditions required for aerospace applications, the passive ModCon aerospace controller can be used.

MPX – Measuring Device for Checking the Mode Distribution

The MPX Modal Explorer is a state-of-the-art measuring device used to characterize the mode distribution in multi-mode fibers, patch cords, or sources and to check their compliance with available standards (e.g. IEC). For this purpose, the light sources are simply connected to the MPX, and the measurement of the mode coupling conditions occurs in real time.

The MPX is used for different applications:

• To characterize sources and patch cords in accordance with IEC11801 and TIA/EIA568 LAN tests
• To identify VCSELs for Gigabit Ethernet IEEE 802.3
• To inspect connectors
• To measure light sources in accordance with IEC 61280-4-1
• To align fiber-coupled light sources
• As a mode scrambler and to characterize mode filters

MPX-SR3 Fiber Shaker

To correctly measure the modal excitation condition of "encircled flux" in multi-mode fibers, so-called fiber shakers are used to prevent or reduce laser speckles in the measurement of laser-based transmission paths according to the industrial standard (IEEE 802.3aq and FOTP-203).

The MPX-SR3 fiber shaker reduces laser speckles by changing the differential path length of the different modes in the fiber. The fiber is continuously moved during measurement to average the speckle effect. This ensures sufficient repetition accuracy for the measurement of the encircled flux. This device has two channels: one channel has an OM1 fiber (a gradient index fiber of 62.5 µm), and the other has an OM2 fiber (a gradient index fiber of 50/125 µm). Each channel is equipped with FC/PC connectors on a standard basis.