With the development of new technologies such as “Internet +”, cloud computing , Internet of Things, and big data, and the full rollout of FTTX and 5G network construction, the demand for optical fiber passive components, especially optical fiber couplers, is increasing rapidly in construction projects. Blowout situation. Optical fiber coupler is an optical device that realizes the distribution or combination of optical signal power between different optical fibers . In its manufacturing process, the fusion tapered method is widely used by optical device manufacturers because of its simple operation, low manufacturing cost, and low device loss. .
With the development of miniaturization of optical passive devices and the increase in cost control requirements, device manufacturers have encountered some new problems when using existing single-mode fibers for devices: using single-mode fibers for device tapering , in a small bending radius environment Under the circumstances, if it is used in small-sized devices such as narrow spaces, corners, distribution boxes or optical splitters, the macrobending loss of optical fiber links is very large, which cannot meet the requirements of practical applications; Although the macrobend loss of insensitive single-mode fiber is very low, in the process of making the coupler, due to the mismatch of the characteristics of the core material (expressed as the mismatch of viscosity and thermal diffusion ratio), it will lead to asynchronous changes in the structure of the fiber waveguide , eventually leading to no matter how to optimize the fused tapered process , the splitting ratio required by the coupler cannot be achieved, and the process loss is very large, so the production of the coupler cannot be completed.
In order to solve the pain points of these industries, on the basis of the existing single-mode fiber for tapered devices (PH1010-B) and bend-insensitive single-mode fiber for devices (PH1011-A), by optimizing the profile parameters and rationally designing normalization frequency, a new bend-insensitive single-mode fiber (PH1010-C) for device drawer tapers has been developed. Especially the customer demand for micro devices.
1) Macro bending loss
optical index of the bend-insensitive single-mode fiber (PH1010-C) for the tapered device fully meets the G.652.D standard, and the macrobending loss is better than the G.657.A1 standard released by ITU-T.
macro-bend test result of PH1010-C in 1550nm band under the condition of φ20mm bending . It can be seen that under the bending diameter of φ20mm and above, the macrobending loss is less than 0.5dB, which is also far lower than the standard stipulated by ITU-T of G.657.A1.
3) Fiber geometry
Compared with ordinary G.652.D optical fiber, PH1010-C optical fiber has better geometric performance. The cladding diameter is 124.5±0.5μm, the fluctuation range is smaller, and the cladding out-of-roundness and core-clad concentricity are better than G The .652.D standard is strict. In addition, in order to better meet the needs of device customers for inserting cores, the center value of the fiber cladding diameter is set to 124.5 μm, which is slightly smaller than the standard fiber 125 μm.
1) Taper performance verification
of tapered performance : During the melting and drawing process of the optical fiber, material defects and changes in the waveguide structure will cause the optical power loss of the device. The verification is to directly evaluate whether the optical fiber is suitable for making a fused tapered optical fiber device according to the size of the optical power loss of the device and the stability of the device. The figure below is the power/loss curve obtained by tapering PH1010-C fiber , which records the change of power/loss with the stretching length from the beginning of stretching to the shutdown of the fiber tapering machine (P1 is the output power of the fiber, EL is the additional loss, CR is the splitting ratio). The verification uses a 1310/1550nm single-mode pump light source, and the loss fluctuation of the PH1010-C fiber is very smooth during the tapering period , and the loss is always lower than 0.1dB.
2) Device Verification
In order to be as close to the actual application as possible, we handed over the optical fiber to a well-known domestic device manufacturer to make a tapered coupler . After packaging, we did a series of reliability tests according to the optical device inspection standard: 1000h dry heat (Dry Heat , DH for short) ), 800 temperature cycles (Temperature Circuit, referred to as TC), straight pull side pull test, under the above conditions to detect the polarization loss change value (PDL) of the device, the PDL is required to be less than 0.2dB. Due to space limitations, we only list four reliability test results as shown in the figure below.
According to the test results fed back by the manufacturer, the above-mentioned devices prepared by using the bend-insensitive single-mode optical fiber PH1010-C for the drawer all meet the requirements of the device indicators. The manufacturer also reported that the PH1010-C optical fiber has lower tapered loss than a certain product provided by a foreign manufacturer, especially in the drawing of Mini size couplers.