A design strategy of the circular photonic crystal fiber supporting good quality orbital angular momentum mode transmission

The Orbital Angular Momentum Modes Supporting Fibers Based on the Photonic Crystal Fiber Structure

“…We also compare the transmission properties of the HE4,1 mode for three C-PCFs [45], in which we can find that C-PCF 3# has the best performance features such as dispersion value, dispersion variation ΔD in C band, confinement loss, and nonlinear coefficient. From C-PCF 1# to C-PCF 3#, the higher the number of air-hole rings that are removed, the lower the values of dispersion, Based on 5 requirements mentioned above, which are essential for stable OAM mode transmission in long distance MDM systems, C-PCF 3# can support up to 42 OAM modes with good transmission features [45], such as good mode field quality, large index separation and flat dispersion over wide bandwidth, low confinement loss, and a low nonlinear coefficient.…”

“…The thickness of the ring core can also influence the effective index separation. The larger the thickness is, the smaller the effective index separation is [45].…”

“…Based on this kind of idea, a circular type PCF was firstly proposed by our research group as shown in Figure 2 [36]. This kind of circular PCF, by optimizing design, can support 14, 26, and 42 good quality OAM modes with satisfied transmission properties like low confinement loss, flat CD, large effective mode area, and low nonlinear coefficient [39,42,43,45]. (a)…”

“…Another advantage is that the smaller value of ρ (the thicker ring area) can be chosen to suppress the coupling between SAM and OAM while keeping more OAM modes during the process of the fiber design. Based on 5 requirements mentioned above, which are essential for stable OAM mode transmission in long distance MDM systems, C-PCF 3# can support up to 42 OAM modes with good transmission features [45], such as good mode field quality, large index separation and flat dispersion over wide bandwidth, low confinement loss, and a low nonlinear coefficient. It is an effective method to increase the number of the OAM modes by changing inner air-hole arrays into ring core area, and hence enlarging the radius of ring area r, by which we also designed C-PCF 1# and C-PCF 2# in the OAM fiber family with different outer ring size, as shown in Table 1.…”

“…Refractive index Silica: n = 1.444, air holes: n = 1.000; n cl = 1.231, (n co /n cl ) 2 We also compare the transmission properties of the HE4,1 mode for three C-PCFs [45], in which we can find that C-PCF 3# has the best performance features such as dispersion value, dispersion variation ∆D in C band, confinement loss, and nonlinear coefficient. From C-PCF 1# to C-PCF 3#, the higher the number of air-hole rings that are removed, the lower the values of dispersion, confinement loss, and nonlinear coefficient are, and the greater flatness of the dispersion over wavelength range is.…”