Science Fair Help: Fiber Optics

[Jverde]

Hello,
I did a project that looked at the affects of macro bending on fiber
optic cables. I injected 1310 nm and 1550 nm wavelengths of light
using a laser into a singlemode and multimode cable. I measured the
power in dbm and I wrapped the cables around varying diameter dowels
with the smallest one having a radius of .32cm. I would wrap it from
0 to twenty wraps in incriments of half wraps. I found that the
multimode cables did not attenuate but the singlemode cables did. I
also noticed that for the singlemode cables the 1550 nm wavelength of
light attenuated significantly more than the 1310 nm wavelength of
light. I was wondering if anybody could give me any advice as how to
explain why the multimode cable had no attenuation and why the 1550 nm
attenuated more than the 1310. Any help or suggestions would be
greatly appreciated. Thank you for your time and help.