Curvature dependence of the effective cutoff wavelength in single-mode fibers

Abstract

Abstruct-The curvature dependence of the effective cutoff wavelength is investigated for both matched-cladding and depressed-cladding fibers. Contrary to the depressed-cladding fiber, the cutoff wavelength of the matched-cladding fiber is strongly curvature dependent. A formula is developed for the bending loss of the first higher-order mode group in a depressed-cladding fiber. By taking into account the effect of the stress-induced changes in the refractive index on the loss the first higher-order mode group, the effective cutoff wavelength as a function of curvature is calculated. The theoretical results show good agreement with measured values, which verify the curvature insensitivity of the effective cutoff wavelength of depressed cladding fibers.

Bit Error Rate Degradation Due to Modal Noise in Single-Mode Fiberoptic Communication Systems

“…(Sim -S 0m ) (16) These calculations require the values of the circuit noise variance, the average gain, and the excess noise factor. For a typical APD at a data rate B = 2Gbit/s these values [15] are σ 2 = 6χ!0" 15 where the excess noise facotr F«M» is given by…”

“…Knowing that the attenuation of the LP n mode a varies from a few hundredths of a dB to a few hundreds of dB per meter [16], the bit error is calculated for the dimensionless loss parameter defined as <x(L) = ocL. If r as the nonzero extinction ratio (NER), defined by b 0 r = - (13) the power in the ON and OFF states bj and b 0 will be given by (14) The bit error rate BER m in presence of modal noise can now be calculated [13,14] as BER, -HS) ( error rate of 10 9 at r = 0.4 is much higher at oc(L) = 10 compared to r = 0.1 and again at a(L) = 25, the excess power needed to maintain the bit error rate approaches zero.…”

“…There are a number of ways in which the modal noise can be reduced [1,7,16]. The obvious one is to make the connector an ideal one with the loss η 0 to be OdB.…”

“…To maintain tight guidance, fibers are operated slightly above cutoff leading to the propagation conditions for the LP U mode if excited in the fiber. Such excitation of the LP U mode becomes a reality from the presence of a nonideal connector [9,[16][17][18][19]. The attenuation constant α is dependent on the cut-off wavelength of the LP 01 mode and the operating wavelength along with the diameter of the fiber and the indices of the core and cladding through the V parameter of the fiber.…”

A Monolithic Dual-Color Total-Internal-Reflection-Based Chip for Highly Sensitive and High-Resolution Dual-Fluorescence Imaging

“…11(a)-(d), there are a high-intensity region in the center excited by the fundamental mode and two much lower intensity regions on two sides of the high-intensity region that might be excited by the second mode. There have been several approaches to filter out the transmission of the higher modes in the single-mode fibers [31], [39], [40]. A small misalignment on the positions of the optical fibers along the longitudinal and vertical axes of the chip could also cause the variation on the size of the TIR fluorescent spots.…”