SLMs for sub-systems and characterisation in SDM (OECC 2014 paper MO1C-1 7th July 2014)

[@joelacarpenter]

Attending The OptoElectronics and Communication Conference and the Australian Conference on Optical Fibre Technology 2014 (OECC/ACOFT 2014) in Melbourne, Australia, 6th-10th July 2014. Talk 2pm Monday (MO1C-1)

[@smsn14]

Hi Joel, I love the videos. Is there a limit to how big a mode can fit into a single mode fiber? Laguerre Gaussian beams for example. Regards,

[@joelacarpenter]

Mahdi Nouri , Thanks Mahdi, by definition a single mode fiber will always only have 1 spatial mode (Gaussian beam). How large that Gaussian beam is will depend on the size of the core of the fiber and the difference between the refractive index of the core region and the cladding region of the fiber (small difference=big beam). If you make the core too big, and/or the refractive index difference too large, then the fiber will start to support higher-order modes and is no longer a single-mode fiber. It is now a few-mode or multimode fiber. More info, www.rp-photonics.com/v_number.html

[@smsn14]

Joel Carpenter, Thank you Joel. Would it theoretically be possible to couple in light that has a smaller wavelength than what a fiber is rated for and be able to get higher order modes into it? Or would that just not work?

[@joelacarpenter]

Mahdi Nouri Sure, when an SMF is rated for a particular wavelength, that's usually just the wavelength range where it's still single-mode. For instance if you couple 850nm light into a SMF for 1550nm, it'll support higher-order modes (LP01 and LP11), if you couple in 660nm it'll support (LP01,LP11,LP02 and LP21). The loss will also be different at different wavelengths, if you go too short, (~2000nm) then the glass won't be transparent anymore and you'll have to use a fibre made of a different material.