Dual-concentric-core Photonic Crystal Fiber Research Articles

All-Solid Photonic Crystal Fiber for Dispersion Compensation Over <inline-formula> <tex-math notation="LaTeX">$S+C+L$ </tex-math> </inline-formula> Wavelength Bands

A dual-concentric-core photonic crystal fiber (DCPCF) with low germanium doping is numerically investigated for dispersion compensation. The inner cladding is formed by a fluorine-doped concentric ring which is used to increase the index slope difference between two supermodes and eliminate the sensitivity of dispersion characteristic to air holes in the inner cladding of traditional structures. The proposed DCPCF can compensate for the dispersion and dispersion slope of a standard single-mode fiber (SMF) at 1550-nm wavelength. The $K$ value matches with that of SMF very well. Moreover, it can realize an effective compensated dispersion range of ±0.8 ps/nm/km from 1.458 to $1.626~\mu \text{m}$ wavelength which covers the $S+C+L$ bands. The geometric parameters on dispersion characteristic are investigated. The sensitivity of the fiber dispersion and the effective compensated dispersion to ±2% and ±5% variation in the optimum parameters is studied for practical fabrication.

Solutions for Modal Squeeze in Dual-Concentric Core Photonic Crystal Fibers

Dual-concentric core photonic crystal fibers (DCC-PCF) were a kind of dispersion compensating fiber with ultrahigh negative dispersion. However, they usually have an undesirable characteristic, called “modal squeeze” in this letter, which causes difficulty in achieving a single-mode operation. This letter discusses a phenomenon of modal squeeze, and proposes a solution to avoid it. Finally, we give designing examples of DCC-PCFs for avoiding the modal squeeze and operating in single mode.

Theoretical investigation of a dispersion compensating photonic crystal fiber with ultra-high dispersion coefficient and extremely low confinement loss

A dispersion compensating photonic crystal fiber (DCPCF) with ultra-high chromatic dispersion coefficient and extremely low confinement loss based on a hybrid structure of dual-concentric core photonic crystal fiber (DCC-PCF), and depressed-clad photonic crystal fiber (DeC-PCF), is theoretically investigated. To enhance the performances with regard to dispersion and confinement loss of the proposed DCPCF, a high refractive index Germanium-doped rod is introduced in the central core. For the sake of comparison, two types of DCPCF published previously were simulated simultaneously in this work. The numeric results reveal that the proposed DCPCF has a dispersion coefficient of −51625ps/kmnm and a confinement loss of 6.54×10−4dB/km at a wavelength of 1.55μm; it undeniably has extremely good performances when compared with the other two types of DCPCF. Moreover, it is worthwhile emphasizing that the proposed structure has an advantage of easy fabrication.

Wavelength-Tunable Dispersion Compensating Photonic Crystal Fibers Suitable for Conventional/Coarse Wavelength Division Multiplexing Systems

A strongly dispersion-compensating and wavelength-tunable photonic crystal fiber (WT-DCPCF) based on a hybrid structure of dual-concentric-core photonic crystal fiber (DCC-PCF) structure and depressed-clad photonic crystal fiber (DeC-PCF) is proposed. To enhance the dispersion compensation effect, a hybrid structure of DCC-PCF and DeC-PCF is used as a basic structure. To vary the operation wavelength, some different index rods with same diameter is inserted into the central core of the hybrid fiber. The numeric results show that the operation wavelength is determined by the refractive index of the central rod, and the proposed WT-DCPCF has high chromatic dispersion coefficients of −39895 to −47179 ps/km·nm at a tuned wavelength range of 1509–1610 nm. The proposed module can be used in conventional/coarse wavelength division multiplexing systems in optical fiber communication networks.

Dual-concentric-core photonic crystal fibers with two layers of outer ring core

To elastically design a dual-concentric-core photonic crystal fiber (DCC-PCF) for dispersion compensation, we use double layers of cladding holes as an outer ring core (ORC), instead of single layer ORC, of the DCC-PCF. For a DCC-PCF with single ORC structure, the design process of maximum dispersion coefficient becomes entangled with that of the compensated wavelength. By using double ORC, the optimum value of chromatic dispersion can be kept when the compensated wavelength is adjusted. The numeric results indicate that the negative chromatic dispersion coefficient for the proposed DCC-PCF is approximately 15 % larger than that of the previous DCC-PCF at around the wavelength of \(1.55\,\upmu \hbox {m}\).

Dispersion compensation properties of dual-concentric core photonic crystal fibers

The dispersion compensation properties of dual-concentric core photonic crystal fibers are theoretically investigated in this letter. The effects of geometric structure on the dispersion properties of dual-concentric core photonic crystal fibers are carefully studied by finite element method. The first layer of holes around the core area is enlarged in a new manner with the near-core point fixed. Considering the tradeoff among several parameters, results show that the dispersion compensation wavelength and strength can be tuned to desired values by constructing an appropriate design of the geometric structure of photonic crystal fibers.

Dispersion ultrastrong compensating fiber based on a liquid-filled hybrid structure of dual-concentric core and depressed-clad photonic crystal fiber

To achieve a dispersion-compensation photonic crystal fiber with an ultralarge negative chromatic dispersion coefficient, this paper theoretically investigates a liquid-filled hybrid structure of dual-concentric core photonic crystal fiber (DCC-PCF) and depressed-clad photonic crystal fiber (DeC-PCF). The proposed hybrid structure reveals an important property: The design can avoid the restriction of “mutual involvement” between two supermodes, thereby significantly increasing the index slope difference between two supermodes. Ultimately, the negative chromatic dispersion coefficient is greatly enlarged. The numeric results indicate that the negative chromatic dispersion coefficient for the proposed hybrid dispersion-compensating PCFs is up to −40400  ps/(km−nm) at a wavelength of around 1.55 μm, which is approximately 1.81 times larger than that of the previous structure.

Large negative dispersion in dual-concentric-core photonic crystal fiber with hybrid cladding structure based on complete leaky mode coupling

Considering the optical stability of solution, the sugar-solution is infused into the outer core ring of dual-concentric-core photonic crystal fiber (DCCPCF). The influences of structure parameters and solution concentration on the phase and loss matching are comprehensively analyzed. By choosing the appropriate outer core mode to completely couple with the inner core fundamental mode, the large negative dispersion PCF around 1.55 μm is designed, which has the dispersion value of − 39,500 ps/km/nm as well as bandwidth of 7.4 nm and effective mode area of 28.3 μm 2. The designed PCF with hybrid cladding structure can effectively compensate the positive dispersion of conventional single mode fiber, and suppress the system perturbation caused by a series of nonlinear effects. Considering the mode field mismatching between the DCCPCF and the tapered fiber, the calculated connection loss around 1.55 μm is below 3 dB. In addition, the equivalent propagation constants of two leaky modes are deduced from the coupled-mode theory, and the complete mode coupling case can be well predicted by comparing the real and imaginary parts of propagation constants.

In-fiber modal interferometer based on dual-concentric-core photonic crystal fiber and its strain, temperature and refractive index characteristics

An in-fiber modal interferometer is demonstrated by splicing a section of homemade dual-concentric-core photonic crystal fiber (DCCPCF) and two segments of single-mode fibers (SMFs) with collapsing the air holes in the splice regions. By analyzing the transmission spectra and the spatial frequency spectra of the interferometers, it's observed that the main interfering modes are the high-order ring modes, which are different from the previously reported interferometers using the single-, few- or multi-mode fibers. The influences of the lengths of DCCPCF and the first collapsed region on the interferometers were investigated experimentally. The strain, temperature and refractive index characteristics of the interferometer were analyzed.

Numerical analysis and optimization of a dual-concentric-core photonic crystal fiber for broadband dispersion compensation

In this article, a novel dual-concentric-core photonic crystal fiber (DC-PCF) for dispersion compensation is presented. The proposed DC-PCF has relatively high negative dispersion over a wide wavelength range, which covers E, S, C, L and U telecommunication wavelength bands. The validity of the proposed design is carried out by employing a 2-D finite difference frequency domain method (FDFD) with perfectly matched layers (PML). By using the numerical method, the dispersion profile of the DC-PCF is optimized in terms of three air-hole diameters to achieve desirable negative dispersion. The influence of the location of ring-core, the number of air-hole rings on dispersion and loss characteristics are also studied.

Reply to Comment on “Design of a broadband highly dispersive pure silica photonic crystal fiber”

A reply to the Comment by Mortensen et al. [Appl. Opt. 47, xxxx-xxxx (2007)] on our previous paper on on our earlier paper published in [Appl. Opt.46, 3263-3268 (2007)APOPAI0003-6935 is presented. In the theoretical study of a highly dispersive dual concentric-core pure silica photonic crystal fiber, we presented a design wherein the high value of the dispersion coefficient was due to coupling of modes between two asymmetric cores at a phase-matched wavelength of 1.55 μm. In the condition in which both the supermodes are excited simultaneously, the dispersion effects of the two modes do not cancel each other, but the final dispersion coefficient depends on the input launching condition. We also predict the feasibility of manufacturing low-loss pure silica dual concentric-core photonic crystal fibers in future with advancement in the current fabrication techniques.