Fiber Splice Loss Research Articles

Proposal for calibration of a single-photon counting detector without the need of input photon flux calibration

A method for calibration of single-photon detectors without the need of input photon flux calibration is presented. The method relies on the use of waveguide-coupled single photon detectors and a series of photon-counting measurements using a single-photon source. It is shown that the method can yield relative uncertainties of less than 1% including counting statistics and fiber splice loss uncertainties with a total measurement time of about 1 h under the assumptions that the fractional losses of the waveguide-coupled detectors are known or zero and the loss along the waveguide is constant. It is also shown that the fractional losses of the waveguide-coupled detectors can be determined if they are equal. However, in this case an input photon flux calibration is required.

Proposal for calibration of a single-photon counting detector without the need of input photon flux calibration

A method for calibration of single-photon detectors without the need of input photon flux calibration is presented. The method relies on the use of waveguide-coupled single photon detectors and a series of photon-counting measurements using a single-photon source. It is shown that the method can yield relative uncertainties of less than 1% including counting statistics and fiber splice loss uncertainties with a total measurement time of about 1 h under the assumptions that the fractional losses of the waveguide-coupled detectors are known or zero and the loss along the waveguide is constant. It is also shown that the fractional losses of the waveguide-coupled detectors can be determined if they are equal. However, in this case an input photon flux calibration is required.

Analysis of Worst-Case Fiber Splice Loss Associated with Mechanical Tolerance

An analysis is presented of optical fiber splice loss associated with mechanical tolerance for coated and uncoated avionic fibers coupled in a loose sleeve (glass capillary). A simple prescription is provided for calculating worst-case loss, combining simultaneous contributions from core offset, core diameter mismatch, numerical aperture mismatch, and core ellipticity. Worst-case values are interpreted with the aid of a Monte Carlo analysis, simulating 10,000 splices. The analysis produces a simple rule of thumb relating the worst-case splice loss to the value exceeded by 1% of the simulated splices: “divide the worst-case loss by 3 to get the 1% value.”

Modeling Dissimilar Optical Fiber Splices With Substantial Diffusion

Optical losses of dissimilar fiber fusion splices are modeled using a combination of diffusion simulation and beam propagation method; open-source codes are provided. It is demonstrated that an optimal amount of diffusion is required to achieve the minimum splice loss. Additional annealing beyond the optimal level is detrimental. Furthermore, oscillation of splice loss with the geometrical parameters of the heat zone due to an optical interference effect is revealed, which can be intentionally utilized to reduce dissimilar fiber splice losses. Understanding these diffusion-related splice loss mechanisms is important for splicing process optimization, as well as design of fusion splicers and novel postsplicing heat treatment devices.

Optical fiber splice loss predictions from one-way OTDR measurements based on a probability model

It is well known that one-way optical time-domain reflectometry (OTDR) measurement contains a false contribution to the splice loss due to statistical fluctuations in light scattering among fibers. Using a large amount of collected data over splice losses from field installations, a two-dimensional probability distribution function with the actual splice loss and the one-way measured OTDR discontinuity as variables was fitted to the data. The five parameters of the chosen probability distribution were determined numerically from the observed data. The probability of keeping the splice loss below a target value based on the observed one-way OTDR reading was calculated and can be displayed in a curve or a table of values. The agreement between theory and experimental values is satisfactory for standard match clad single-mode fibers measured at 1.3- mu m wavelength. >

Multimode optical fiber splice loss: Relating system and laboratory measurements

We examine the splice loss occurring along a multimode fiber regenerator span and compare the results to a "standard" laboratory test condition. Large variations in the splice loss sensitivity to transverse offset of a "reference" splice were seen 1) at the ends of 5 different 8.9-km fiber concatenations and 2) at various locations along one 8.9-km path. These data indicate that significant variations in the modal power distribution exist even at the receiver end of a regenerator span. This is explained by the long coupling lengths (long compared to splice spacing) of low loss fibers and the random amount of mode coupling introduced by the concatenation splices. Splice loss measurements made with an "overfilled" launch condition and a 3-turn 20-mm mandrel wrap mode filter (commonly used in fiber loss measurements) accurately approximated the average splice loss sensitivity along the span for offsets less than 4 μm. i.e., losses less than 0.2 dB. For offsets greater than 4 μm, the mandrel wrap mode filter configuration yields a pessimistic estimate, but is within 30 percent of the average "system" loss for most cases of interest. This demonstrates the usefulness of the mode filter in establishing splice measurement conditions that yield results representative of those seen in a regenerator span.

Misalignment losses at multimode graded-index fiber splices and GRIN rod lens couplers

A geometric optics model to describe transverse offset splice loss in multimode graded-index fiber, which has been adapted to evaluate misalignment losses at a graded-index rod (GRIN rod) lens-to-lens coupler, is reported. In both cases, the model gives close agreement with experimental measurements. Finally, in contrast with fiber splice losses, invariance of the lens coupler loss with the optical launch and receive conditions is shown.

A General Characterization of Splice Loss for Multimode Optical Fibers

The Gaussian point transmission model for calculating optical fiber splice loss is extended to the general case of splice loss between fibers which differ in one or more intrinsic parameters–core radius, index of refraction profile shape, and maximum index of refraction difference between core and cladding. The model is first verified for splices with index-of-refraction, profile mismatch. The average difference between calculated and measured splice loss due to profile parameter mismatch is 0.04 dB. Comparisons are also made between calculated and measured splice loss for ten different splices with mismatch in all three intrinsic parameters. The average difference between the calculated loss and the average of several measured losses for these ten cases was 0.06 dB. The additional losses introduced by transverse offset measured for one set of mismatched fiber splices agree with the calculated values within 0.1 dB. Loss due to misalignment of elliptical core fibers is calculated and measured with agreement within 0.06 dB for the maximum toss case. Both the model and the experimental data show that, for a given percentage mismatch, index of refraction profile parameter mismatch and core ellipticity contribute significantly less to splice loss than mismatch of core radius or numerical aperture. A family of curves for splice loss vs transverse offset is presented for various numerical aperture mismatches and core radius mismatches, since these parameters are typically the largest components of splice toss in practical fiber optic systems.