Home Forums GENERAL Modes classification

Modes classification

Profile Photo
(joined November 2014)
Participant

Dear Friends,

In Spatial CW laser we have two options of modes which is Hermite-Gaussian modes and Laguerre-Gaussian modes. but in most of the mode division multiplexing papers I have seen they are only talking about LP modes for transmission of data. What is the reason of this?

Responses (3):

    • #28150
      Profile Photo
      Aadil Raza
      Participant

      Dear Friends,

      In Spatial CW laser we have two options of modes which is Hermite-Gaussian modes and Laguerre-Gaussian modes. but in most of the mode division multiplexing papers I have seen they are only talking about LP modes for transmission of data. What is the reason of this?

    • #28157
      Profile Photo
      Steve Dods
      Participant

      LP modes (Linear Polarized modes) are popular for use as an approximation to propagation on weakly guiding optical fibres. The real modes are vector modes that have complicated field patterns, but the refractive index of an optical fibre core is usually only a fraction of a percent higher than the cladding. Because of this small contrast, the vector modes are almost linearly polarized, and so the LP approximation is pretty good for most optical fibres.

      Propagation in free space, such as in the cavity of a gas laser, is a different thing. The Gaussian modes are appropriate for that case.

    • #28181
      Profile Photo
      Aadil Raza
      Participant

      Thanks for reply. So it means we have to generate LP modes for data modulation and then transmit them in optical fiber for MDM? or we can also use Hermite-Gaussian modes and Laguerre-Gaussian modes for this purpose as well? please clear my confusion. secondly if fiber support only lp modes then why we have Hermite-Gaussian modes and Laguerre-Gaussian modes in spatial CW laser? waiting for your reply please..

    • #28225
      Profile Photo
      Steve Dods
      Participant

      The mode is the form the wave assumes when it follows a waveguide. Different waveguide, different mode. Typical optical fibres have LP modes. Free space, such as in gas laser cavity, the Gaussian modes are better for the model. Integrated optical devices will have different modes. Light in one mode can pass into another, but usually with some coupling loss.

Login You must be logged in to reply to this topic.