Fused Fiber Couplers Research Articles

Incident polarization angle and temperature dependence of polarization and spectral response characteristics in optical fiber couplers

The incident polarization angle and temperature dependence of the polarization and spectral response characteristics of three different types of fiber coupler are presented. The couplers are (1) the biconicalfused- twisted-taper single-mode fiber (coupler A), (2) the asymmetric-etched-fused-taper wavelength division multiplex (coupler B), and (3) the biconical-polished polarization maintaining fiber (coupler C), respectively. It is confirmed experimentally that the polarization characteristics of couplers A and B vary greatly with temperature, but those of coupler C are independent of temperature. Also, the wavelength dependence characteristics of the power splitting ratio of couplers B and C have almost no change with temperature. However, the wavelength dependence of coupler A is greatly changed with temperature. Comparing couplers A and B, it is postulated that the sinusoidal variations of the polarization state vs the incident polarization angle are due to the stress birefringence caused by the fiber twisting when the fused fiber coupler is fabricated and packaged.

Monolithic wavelength-flattened 1 × 7 single-mode fused fiber couplers: theory, fabrication, and analysis

The basic theory of monolithic 1 x 7 couplers is presented. The results of fabricating eighty-two devices are described, and the steady improvement in achieved device performance is shown leading to the fabrication of a controlled batch of eleven devices. These devices have excess losses of <0.1 dB together with good coupling uniformity to the seven output fibers. Maximum insertion losses are all around 10 dB or less, which is seen to compare favorably with devices obtained by concatenating 2 x 2 couplers. It is shown that to obtain an equal power split between the center and outer fibers it is necessary to control carefully the degree of fusion of the structure. An analysis of this coupling behavior is presented.

Polarization properties of fused fiber couplers and polarizing beamsplitters

The polarization properties of fused taped fiber couplers were investigated experimentally by changing cross-sectional shapes at the coupler waist. The coupling difference between x and y polarized light was studied for many test fused fiber couplers with various cross-sectional shapes. On the basis of the experimental results, two polarizing beamsplitters with the aspect ratio of 1.1 and 1.8 were produced, and their chromatic characteristics were measured. It was evident that the aspect ratio should be more than 1.7 to manufacture polarizing beamsplitters with few power transfer cycles, i.e. long spectral period. Splitting ratios of polarizing beamsplitters with the aspect ratio of 1.1 and 1.8 were 17.6 and -12.7 dB for x polarized light and -16.1 and 11.7 dB for gamma polarized light, respectively. Their losses were less than 0.6 and 0.3 dB. >

7×7 monolithic single-mode star coupler

The operating principle and fabrication of a single-mode, 7×7 monolithic star coupler is reported. The device exhibits low excess loss of 0.14 ± 0.006 dB together with good coupling uniformity. The mean insertion loss at 1300 nm is 8.62 dB with a standard deviation of 0.52 dB. The device is fibre compatible and similar in size to a standard 2×2 fused fibre coupler.

Fused taper couplers in multimode fluorozirconate fibre

Fused fibre couplers, an important component of all present silica based fibre systems, have been fabricated in multimode fluoride fibres for the first time. Coupling ratios of 20-40% and excess losses of <2 dB were obtained over a wide wave-length range in a packaged device.

Performance tuning of 1×7 wavelength-flattened fused fibre couplers

In order to successfully fabricate monolithic 1×7 wavelength-flattened couplers, careful control over the degree of fusion of the structure is required. The variation of coupling characteristics with the degree of fusion is discussed. Two degrees of fusion are identified where an equal power split wavelength-flattened response may be obtained.

Analysis of mode coupling behavior in fused polarization-maintaining fiber couplers

To achieve low excess loss fiber couplers, analysis on mode coupling behavior in fused fiber couplers has been carried out using a combination of a scalar wave finite element method and a step approximation method, with an emphasis on clarifying the excess loss mechanism in fused polarization-maintaining (PANDA) fiber couplers. Numerical analysis has indicated the following results: First, fused PANDA fiber couplers have a critical outer diameter in the biconical taper region,, at which mode couplings between the symmetric fundamental mode and the symmetric next higher-order mode take place. Second, PANDA fiber couplers in which the waist diameter in the biconical taper region is larger than the critical diameter have small excess loss, because the large waist diameter provides the small mode coupling, although too large a waist diameter does not allow power splitting as a coupler. This analysis shows that excess loss in PANDA fiber couplers largely depends on the outer diameter dimension of the biconical taper region and gives an optimal value of such diameter. This is in good agreement with the experimental results.

Broadband all-fiber filters for wavelength division multiplexing application

In-line spectral filters are designed and realized using the tapering technique to provide additional isolation to the demultiplexing fused fiber couplers. The typical performances obtained are less than 1 dB loss with more than 15 dB isolation in a 40 nm range around the desired wavelengths.

Fibre laser with adjustable fibre reflector for wavelength tuning and variable output coupling

Fibre-loop reflectors are applied to Nd3+ doped fibre lasers operating in the 4F3/2→4I11/2 transition. The splitting ratio of the fused fibre coupler used in a loop reflector is varied thermo-optically, giving rise to a spectral variation in the reflectivity of the device. Using the fibre loop in a configuration with a broadband dielectric mirror to form a resonant cavity, we demonstrate wavelength tuning of the fibre laser and continuously variable power output for a constant pump power.

Coupling model for fused fiber couplers with parabolic taper shape

An analytic coupling model for fused fiber couplers is obtained assuming a parabolic taper shape for the fibers. The model is compared to experimental results for several fused fiber couplers. Both pull length and final fiber diameter can be predicted for 3-dB couplers.

Loss mechanisms in single-mode fiber tapers

The onset of transmission loss in four single-mode tapers is shown to coincide with the taper slope exceeding the critical slope angle at which fundamental mode cutoff occurs. This implies that the primary loss mechanism in single-mode fiber tapers is cutoff of the fundamental mode from the core. A secondary loss mechanism of coupling to the modes of a coaxial outer waveguide is also observed and modeled. Implications for fused fiber couplers are discussed.

Polarisation-maintaining fibre couplers with low excess loss

Polarisation-maintaining fused fibre couplers with excess loss of less than 0.1 dB have been fabricated by using polarisation-maintaining and absorption-reducing (PANDA) fibres with matched-index stress-applying parts. The couplers show polarisation crosstalk of less than ?30 dB.

Polarisation characteristics of fused-fibre coupler as quarter-wave device in 1.55μm-wavelength region

Polarisation characteristics of the fused-taper-twisted single-mode-fibre coupler as a quarter-wave device are reported for the first time. In the case that circular polarisation is launched into the input port of the fused-fibre coupler, linear polarisation was observed at two output ports of the coupler, and an extinction ratio of about 30dB was obtained.

Some particular properties of monomode fused fiber couplers

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Jacques Bures, Suzanne Lacroix, Christian Veilleux, and Jean Lapierre, "Some particular properties of monomode fused fiber couplers," Appl. Opt. 23, 968-969 (1984) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Fabrication of polarisation-maintaining [3×3] single-mode-fibre couplers

[3×3] fused fibre couplers have been fabricated with polarisation-maintaining and absorption-reducing (PANDA) fibres. The couplers can hold linear polarisation along the principal axis of the fibre branches, showing an extinction ratio better than −15 dB.