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These polarization-maintaining (PM) fiber optic patch cords utilize dispersion-compensating fiber (DCF) and are suitable for applications requiring precise control of system dispersion. As shown in the figure, both ends of the DCF are fused to a short section of PM1550-XP fiber to minimize losses when connected to other PM patch cords. Both ends use narrow-key ceramic ferrule FC/APC connectors. These patch cords undergo high-quality polishing and have a typical return loss of 60 dB. Each patch cord is assembled in our factory and individually tested at 1550 nm wavelength to ensure its extinction ratio and insertion loss meet specifications. Each patch cord comes with a datasheet summarizing the test results.
Features
● Dispersion and Dispersion Slope Exactly Compensate 2, 5, or 10 m of PM1550-XP Fiber
● Narrow Key (2.0 mm) Aligned to Slow Axis
● Typical Return Loss of 60 dB
● Ceramic 8° Angled Ferrules (APC)
● Ø3 mm Protective Outer Jacket
● Individual Test Report Included with Each Cable;
● Click Here for Sample Data Sheet
● Operate Between 1510 nm and 1620 nm
● Compensates for Both Dispersion and Dispersion Slope
● Polarization-Maintaining Fiber with FC/APC Connectors on Both Ends
Specification
| Item # | PMDCFA2 | PMDCFA5 | PMDCFA10 |
|---|---|---|---|
| Operating Wavelength | 1510 - 1620 nm | ||
| Cutoff Wavelength | 1400 nm | ||
| Cable Fiber Type | PMDCF with Two Short Sections of PM1550-XP Spliced to Each End (PANDA) | ||
| Cable Length | 0.70 ± 0.05 m | 1.20 ± 0.05 m | 2.05 ± 0.05 m |
| Compensated Fiber | 2 m of PM1550-XP | 5 m of PM1550-XP | 10 m of PM1550-XP |
| Total Dispersion | -0.034 ± 0.004 ps/nm | -0.085 ± 0.009 ps/nm | -0.175 ± 0.018 ps/nm |
| Total Dispersion Slope | -1.1 x 10-4 ± 0.1 x 10-4 ps/nm2 | -2.8 x 10-4 ± 0.2 x 10-4 ps/nm2 | -6.2 x 10-4 ± 0.4 x 10-4 ps/nm2 |
| Insertion Loss | <2.5 dB | ||
| Extinction Ratio | >19 dB | ||
| Optical Return Loss | 60 dB (Typical) | ||
| Connector Type | FC/APC | ||
| Key Width | 2.00 mm ± 0.02 | ||
| Key Alignment Type | Narrow Key Aligned to Slow Axis | ||
| Jacket Type | FT030-BLUE | ||
| Operating Temperature | 0 to 70 °C | ||
| Storage Temperature | -45 to 85 °C | ||
1550 nm PM DCF FC/APC Patch Cable
| Item # | Cable Fiber Type | Cable Length | Operating Wavelength |
Cutoff Wavelength |
Extinction Ratio |
Insertion Loss |
Total Dispersion | Compensated Fiber Type |
Compensated Length |
|---|---|---|---|---|---|---|---|---|---|
| PMDCFA2 | PMDCF (PANDA) | 0.70 m | 1510 - 1620 nm | 1400 nm | >19 dB | <2.5 dB | -0.034 ± 0.004 ps/nm | PM1550-XP (PANDA) | 2 m |
| PMDCFA5 | 1.20 m | -0.085 ± 0.009 ps/nm | 5 m | ||||||
| PMDCFA10 | 2.05 m | -0.175 ± 0.018 ps/nm | 10 m |
Dispersion in Optical Fiber
Chromatic dispersion, D, in an optical fiber occurs when the group velocity and phase velocity of an optical pulse depend on the optical wavelength/frequency. It is primarily the sum of two components, material dispersion and waveguide dispersion:
Material dispersion arises from the change in a material's refractive index with wavelength, which changes the propagation velocity of light as a function of wavelength. Waveguide dispersion is a separate effect, arising from the geometry of the fiber optic waveguide. Waveguide properties are also a function of wavelength; consequently, changing the wavelength affects how light is guided in a single-mode fiber. For example, decreasing the wavelength will increase the relative waveguide dimensions, causing a change in the distribution of light in the cladding and core.
Another useful parameter is the dispersion coefficient, β, which is also called the phase constant or mode-propagation constant when featured in the nonlinear Schrodinger equation. If the optical pulse propagates along a fiber of length, L, then the associated phase shift is defined as:
β can be expanded to include higher-order nonlinear modes, βi. In particular, the second-order and third-order propagation constants are related to dispersion by:
Where dDfiber/dλ is known as the dispersion slope, which can be positive, negative, or zero, and written as:
Group velocity dispersion (GVD) is the temporal pulse broadening due to different group velocities, and it has significant influence on optical pulse widths on the order of picoseconds or shorter. The group velocity, vg, can be defined as the rate at which the entire pulse envelope will propagate:
Which allows the group velocity dispersion to be defined as:
There is no change in the shape of the temporal pulse when GVD equals zero, however there will always be temporal broadening when GVD is nonzero. When the GVD is greater than zero, the longer wavelength components will propagate faster than the shorter wavelengths; and when the GVD is less than zero, the longer wavelength components will propagate more slowly.
Polarization-mode dispersion (PMD) in typical single-mode fiber occurs as a result of birefringence in the fiber due to asymmetries in fiber stress and geometry. In the frequency domain, it presents itself as a linear change in a fixed input polarization with respect to frequency. In the time domain, it presents itself as the mean time delay of a pulse propagating along the fiber. The group delay is the difference between the mean arrival times at the fiber input and the fiber output.
Polarization-state pairs (PSP) are orthogonal pairs of polarization states at the optical fiber input. For polarization-maintaining fibers, these are the fiber's fast and slow axes, which are treated separately and generally have different phase shifts and group delays. The differential group delay (DGD) is the difference in group delay between the orthogonal pairs of polarization states. DGD increases proportionally to the square root of the fiber length. Polarization-mode dispersion can be defined as a vector that has a magnitude equal to the DGD and points in the direction of the slow axis.
Dispersion-Compensating Fiber
Since dispersion is inevitable in optical fibers, dispersion-compensating fibers (DCF) can be incorporated into optical systems. The overall dispersion of these fibers is opposite in sign and much larger in magnitude than that of standard fiber, so they can be used to cancel out or compensate for the dispersion of a standard single-mode or polarization-maintaining fiber. A negative dispersion slope enables effective cancellation of dispersion over a larger wavelength range, since the dispersion slope of standard fiber is usually positive. Generally, a short length of DCF is spliced into a longer length of standard fiber to compensate for dispersion, as shown in Figure.
Dispersion Compensation Schematic
The dispersion-compensating fiber should be selected to match the dispersion of a regular SM or PM fiber, not only at a single wavelength, but over the whole spectral range of the optical pulse. This means that the DCF should match not only the dispersion, D, but the dispersion slope, dDfiber/Dλ. The ratio of these two factors is called the relative dispersion slope. Similarly, the ratio β2/β3 can be used as another numerical parameter to optimize fiber selection. The more similar these parameters are for the DCF and the standard fiber, the less distorted and impaired the transmitted optical pulse will be at the spliced fibers' output.
To determine the optimal length for a DCF using these matching conditions, one can solve the following coupled equations using the dispersion parameters at the selected wavelength:
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