Causes of confusion in ODF fiber jumping
There are two main reasons for the confusion of ODF fiber jumper layout: product design defects and engineering design deviations.
product design flaws
The current mainstream ODF size is 2200×840×300 (height×width×depth, mm), and the capacity is 648 cores. The space on the left side of the frame is the fiber coil unit, where the remaining length of the fiber jumper is coiled; this space is also the only channel for the fiber jumper to be laid out, whether it is inside the rack or between racks (from other equipment or ODF to this ODF) ) jumpers must be routed through this channel.
If 2/3 of the capacity of the ODF rack is used for intra-rack connections (one jumper fiber is connected to every two ports), and 1/3 of the capacity is used for inter-rack connections, then a maximum of 432 jumper fibers will be deployed. Let's imagine what it would be like if all 432 jumpers were laid out from the space on the left side of the ODF!
engineering design deviation
According to the size of ODF, the maximum length of the fiber jumper in the frame should not exceed 3m, the length of 70% of the fiber jumper should not exceed 2.5m, the length of 40% of the fiber jumper should not exceed 2.0m, and even a small amount of fiber jumper length only needs 1.5m m is enough. However, the fiber jumper lengths listed in our design documents are basically 3.0m in length, and the average excess length of each jumper fiber exceeds 0.5m.
The diameter of the fiber jumper is 2.0mm or 1.2mm, and the performance indicators meet the requirements of use, but almost all the designed and configured jumpers are 2.0mm in diameter.
Such a scene occurs when the number of too long and thick fiber jumpers increases.
Design concept of MODF
The design of MODF adopts the design concept of cable main distribution frame (MDF), and the frame is divided into line side and equipment side. The fiber core of the external optical cable is terminated on the line side, and the end of the optical fiber connected to the port of the equipment is on the equipment side. The jumper jumps from the corresponding equipment port on the equipment side to the corresponding external optical fiber core on the line side.
The MODF disk fiber unit is set on both sides of the frame body, which is also the channel for the fiber jumper to be routed from the equipment side to the line side. Of course, no matter how large the capacity of the fiber coil unit is, it cannot meet the extra length requirement of several meters for each fiber jumper in the design. Therefore, in order to deal with those sloppy designers, MODF has designed a matching fiber storage rack.
When the MODF contains multiple racks, in order to facilitate the placement of fiber jumpers between racks, one side (device side) or both sides of the MODF is provided with a horizontal channel for jumper fibers.
Main types of MODF
In terms of the welding position of the external optical cable, MODF is mainly divided into: final fusion separation type and final fusion integration type.
final melting separation type
The MODF frame of the final fusion separation type is composed of two types of frames: the fusion frame and the terminal frame. The external optical cables are spliced at the splicing frame and terminated at the line side of the terminal frame.
The size of the splicing frame is: 2200×900×300 (unit: mm), and the capacity is 1728 cores. Generally, 2 splicing frames are installed back to back. The size of the terminal rack is: 2200×900×600 (unit: mm), and the capacity is 1152 cores (576 cores on the line side and equipment side); the number of terminal racks is generally 2 to 3 for the first time, and then increased according to the demand. 2 back-to-back fusion splice racks correspond to a maximum of 6 terminal racks.
The final melting separation type MODF is mainly used for the station with a large final capacity, such as the core node. However, there is a certain proportional relationship between the setting of the welding frame and the terminal frame, and the expansion is limited to a certain extent. The advantage is that the terminal frame does not need to lay the lightning protection ground wire.
The design concept of MODF is not to increase the capacity density of ODF, but to facilitate the management of fiber jumpers. But we still need to pay attention to 2 points in engineering design:
(1) Try to configure fiber jumpers of appropriate length according to the needs, and do not leave too much excess length.
(2) Try to use φ1.2mm jumper fiber instead of φ2.0mm jumper fiber.
