**7. Optical connectors**

#### **7.1. Single fiber connectors**

This chapter will give a summary of the optical connectors used today. There are several dif‐ ferent types of connectors used for single mode and for multimode operation. Additionally, there are straight polished types and slant polished ones, which are used in high speed opti‐ cal communication systems because of their high reflection loss characteristics. Further on, connectors are used in various applications including:


**Figure 14.** Fiber-chip connection with flip-chip.

430 Optoelectronics - Advanced Materials and Devices

**Figure 15.** Photograph of flip-chip bonded laser array(Heinrich-Hertz-Institute, Berlin).

**Figure 16.** Concept for a complete optical motherboard [1], [17].



**Table 1.** Optical connectors summary.

All loss failure mechanisms that can be acknowledged at the fiber to fiber coupling are also detectable at connector-connector coupling. All possible losses are depicted in figure 17. On‐ ly highly precise mechanical feed and exact surface polishing can avoid high loss at the con‐ nection. Intrinsic losses can be avoided by using matching fibers, while extrinsic losses can be overcome by strong mechanical feed. Today feeder elements with better than 2 μm lateral deviation are commercially available. Polishing and cleaning the connector surface can avoid absorption and the scattering of the optical power. With the help of anti reflection coatings or angled surfaces, reflections can be (7°-8° degrees) overcome. All connectors are very similar in their mechanical structure. The fiber is fed through a ferrule made of ceram‐ ics, which centers the fiber. Than the ferrule is filled with UV-curing glue. After hardening, the end of the fiber is cut and polished. The outer diameter of the normally used ferrule is 2.5mm or 1.25mm. In figure 18 a cross section of a connector is depicted.

In the following, typical connectors used today are listed in table 1.

The most popular connector today is the FC/PC one direct followed by the Diamond E2000 and the very small SC connector. FC/PC-connectors (see figure 19) are mostly used in optical equipment but have the disadvantage to be easily soiled with dust and dirt. The E2000 is used by several Telecoms because of the integrated dust cover and beam shutter.

**Figure 19.** Optical FC/PC connector.

**7.2. Multi-fiber connectors**

**Figure 20.** Multi-fiber MT-connector.

These types of connectors are often used for the connections of mainframes or servers and at Fiber Distributed Data Interface (FDDI) links. Here the data were transmitted via several op‐ tical data links between the server stations with up to 10 Gbit/s per link. Also multi-sensor systems are using these kinds of connectors. Commercial available types are listed in table 2.

Opto-Electronic Packaging http://dx.doi.org/10.5772/51626 433

The most commonly used connector is the MT one which is depicted in figure 20.

**Figure 17.** Loss mechanisms at connector end surface.

**Figure 18.** Cross section of an optical connector.

**Figure 19.** Optical FC/PC connector.

All loss failure mechanisms that can be acknowledged at the fiber to fiber coupling are also detectable at connector-connector coupling. All possible losses are depicted in figure 17. On‐ ly highly precise mechanical feed and exact surface polishing can avoid high loss at the con‐ nection. Intrinsic losses can be avoided by using matching fibers, while extrinsic losses can be overcome by strong mechanical feed. Today feeder elements with better than 2 μm lateral deviation are commercially available. Polishing and cleaning the connector surface can avoid absorption and the scattering of the optical power. With the help of anti reflection coatings or angled surfaces, reflections can be (7°-8° degrees) overcome. All connectors are very similar in their mechanical structure. The fiber is fed through a ferrule made of ceram‐ ics, which centers the fiber. Than the ferrule is filled with UV-curing glue. After hardening, the end of the fiber is cut and polished. The outer diameter of the normally used ferrule is

The most popular connector today is the FC/PC one direct followed by the Diamond E2000 and the very small SC connector. FC/PC-connectors (see figure 19) are mostly used in optical equipment but have the disadvantage to be easily soiled with dust and dirt. The E2000 is

used by several Telecoms because of the integrated dust cover and beam shutter.

2.5mm or 1.25mm. In figure 18 a cross section of a connector is depicted.

In the following, typical connectors used today are listed in table 1.

**Figure 17.** Loss mechanisms at connector end surface.

432 Optoelectronics - Advanced Materials and Devices

**Figure 18.** Cross section of an optical connector.

#### **7.2. Multi-fiber connectors**

These types of connectors are often used for the connections of mainframes or servers and at Fiber Distributed Data Interface (FDDI) links. Here the data were transmitted via several op‐ tical data links between the server stations with up to 10 Gbit/s per link. Also multi-sensor systems are using these kinds of connectors. Commercial available types are listed in table 2. The most commonly used connector is the MT one which is depicted in figure 20.

**Figure 20.** Multi-fiber MT-connector.


**Table 2.** Optical multi-fiber connectors.
