**8. Modules**

This chapter will summarize several types of modules, which are used in commercial stand‐ ard opto-electronic packages. These can be divided into four basic categories:

**Figure 21.** Direct attach of an optical fiber to a photo diode.

**Figure 22.** Fiber-chip coupling by a two-lens system.

**Table 3.** Alignment precision for one dB additional coupling loss.

low-priced transmitter modules for single mode operation.

**8.4. Transmitter and receiver modules**

**Coupling technique (Laser-fiber)**

In section 3 it has been demonstrated that a single mode butt fiber coupling to a Laser diode can have only 10 % efficiency. But with a lens system, which adapts the different optical mode fields, 50 % to 90 % coupling efficiency can be achieved (see figure 22). Table 4 gives a view of the mechanical aspects for coupling efficiencies with several coupling designs.

**Alignment precision (µm) for 1 dB add. loss at lateral/**

Transmitter modules for low cost applications are normally designed for simple butt fiber to chip coupling without temperature control of the emitting OEIC. Today more lensed cou‐ pling arrangements fixed by laser welding are often introduced. In figure 23, a coaxial cou‐ pled receiver module for high data rates of 40Gbit/s is depicted. This set-up is also used in

**Coupling loss (dB)**

Opto-Electronic Packaging http://dx.doi.org/10.5772/51626 435

**longitudinaldisplacement**

Butt fiber (50µm) 15/50 7-10 Butt fiber (9µm) 2/20 7-10 System with one lens 0,5/5 3 Double lens system 0,5/5 1-3 Fiber taper 0,3/3 3-5

**8.3. Singlemode-fiber coupling**


Each category will be demonstrated by an example, but first some words about the required coupling method.

#### **8.1. Fiber-chip coupling in modules**

The performance of an optical coupling and the affordable operating expense are strongly dependent on the coupling device and the fiber used. The performance is directly corre‐ lated to the coupling efficiency. All commercial implementations are a trade off between cost and efficiency. To reach a very good efficiency you have to invest much manpower, which must be reflected in the price of the product. On the mass market only very low cost modules are available. That's the reason why here only modules with very low cou‐ pling efficiency can be found. The coupling of devices to multi mode fibers is less expen‐ sive than to single mode fibers, which are also priced lower than fiber-taper couplers. These are on the other hand are cheaper than lens-couplers, because of the time effort re‐ quired to adjust additional coupling devices.

#### **8.2. Multimode fiber coupling**

The multimode fiber has an diameter of 50μm and a numerical aperture of 0.25 (15° aper‐ ture). Usually this type of coupling is used in photodiode modules where the fiber is direct‐ ly connected to the photo-absorbing surface of the diode, which is depicted in figure 21.

**Figure 21.** Direct attach of an optical fiber to a photo diode.

#### **8.3. Singlemode-fiber coupling**

**Name Losses Straight**

434 Optoelectronics - Advanced Materials and Devices

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

**1.** Transmitter (laser) -modules w/o cooling

**3.** Transceiver modules (Transmitter/Receiver)

**2.** Receiver (photodiode) -modules

**4.** Passive devices (sensor) -modules

**8.1. Fiber-chip coupling in modules**

quired to adjust additional coupling devices.

**8.2. Multimode fiber coupling**

**8. Modules**

coupling method.

**polished**

**Single (SM) Multi (MM) mode**

FDDI M 0.5dB 0,5dB -20dB -20dB MMSM "/500"/500 WDM med MTConnect 0.3dB 0,5dB -25dB -25dB MMSM "/200"/200 WDM high

This chapter will summarize several types of modules, which are used in commercial stand‐

Each category will be demonstrated by an example, but first some words about the required

The performance of an optical coupling and the affordable operating expense are strongly dependent on the coupling device and the fiber used. The performance is directly corre‐ lated to the coupling efficiency. All commercial implementations are a trade off between cost and efficiency. To reach a very good efficiency you have to invest much manpower, which must be reflected in the price of the product. On the mass market only very low cost modules are available. That's the reason why here only modules with very low cou‐ pling efficiency can be found. The coupling of devices to multi mode fibers is less expen‐ sive than to single mode fibers, which are also priced lower than fiber-taper couplers. These are on the other hand are cheaper than lens-couplers, because of the time effort re‐

The multimode fiber has an diameter of 50μm and a numerical aperture of 0.25 (15° aper‐ ture). Usually this type of coupling is used in photodiode modules where the fiber is direct‐ ly connected to the photo-absorbing surface of the diode, which is depicted in figure 21.

ard opto-electronic packages. These can be divided into four basic categories:

ESCON 0.5dB -20dB MM "/500 LAN,Comp.

**durability (insertions)**

**User Price**

low

Network

In section 3 it has been demonstrated that a single mode butt fiber coupling to a Laser diode can have only 10 % efficiency. But with a lens system, which adapts the different optical mode fields, 50 % to 90 % coupling efficiency can be achieved (see figure 22). Table 4 gives a view of the mechanical aspects for coupling efficiencies with several coupling designs.

**Figure 22.** Fiber-chip coupling by a two-lens system.


**Table 3.** Alignment precision for one dB additional coupling loss.

#### **8.4. Transmitter and receiver modules**

Transmitter modules for low cost applications are normally designed for simple butt fiber to chip coupling without temperature control of the emitting OEIC. Today more lensed cou‐ pling arrangements fixed by laser welding are often introduced. In figure 23, a coaxial cou‐ pled receiver module for high data rates of 40Gbit/s is depicted. This set-up is also used in low-priced transmitter modules for single mode operation.

**Figure 25.** Monolithically integrated transceiver module.

sented by [2], which can be seen in figure 27.

Typical housings are shown in figure 26.

**Figure 26.** Fiber Bragg grating module.

centered into a metal or plastic tube and fixed with special glue.

These kind of modules are normally very easy to fabricate. Bragg sensors are used in a very wide spectrum of applications such as temperature sensors and strain gauge. The grating is

Opto-Electronic Packaging http://dx.doi.org/10.5772/51626 437

Other passive devices use multiple fiber ports which can be combined in an array. Typical array devices are arrayed waveguide gratings (AWG)for multi wavelength optical transmis‐ sion systems. These OEICs must be connected to up to 64 IO-ports at both chip sides as pre‐

**8.6. Sensor and passive devices modules**

**Figure 23.** Receiver module.

**Figure 24.** Temperature controlled laser module with fiber-taper coupling.

For high bit rate optical communications systems, cooled laser devices are needed. These modules are much more complicated in their mechanical set-up which is shown in figure 24. Here a tapered fiber was adjusted in front of the OEIC which is temperature stabilized by a Peltier cooler and a temperature sensor (thermistor) shown by [18].

#### **8.5. Transceiver modules**

These kind of modules are used in optical transmission systems where both terminals of the communications line can talk at the same time, which is called bi-directional communica‐ tion. Transmitter and receiver functions must be integrated in these modules, which are shown in figure 25.

**Figure 25.** Monolithically integrated transceiver module.

#### **8.6. Sensor and passive devices modules**

**Figure 23.** Receiver module.

436 Optoelectronics - Advanced Materials and Devices

**8.5. Transceiver modules**

shown in figure 25.

**Figure 24.** Temperature controlled laser module with fiber-taper coupling.

Peltier cooler and a temperature sensor (thermistor) shown by [18].

For high bit rate optical communications systems, cooled laser devices are needed. These modules are much more complicated in their mechanical set-up which is shown in figure 24. Here a tapered fiber was adjusted in front of the OEIC which is temperature stabilized by a

These kind of modules are used in optical transmission systems where both terminals of the communications line can talk at the same time, which is called bi-directional communica‐ tion. Transmitter and receiver functions must be integrated in these modules, which are These kind of modules are normally very easy to fabricate. Bragg sensors are used in a very wide spectrum of applications such as temperature sensors and strain gauge. The grating is centered into a metal or plastic tube and fixed with special glue.

Other passive devices use multiple fiber ports which can be combined in an array. Typical array devices are arrayed waveguide gratings (AWG)for multi wavelength optical transmis‐ sion systems. These OEICs must be connected to up to 64 IO-ports at both chip sides as pre‐ sented by [2], which can be seen in figure 27.

Typical housings are shown in figure 26.

**Figure 26.** Fiber Bragg grating module.

figure 28. Additionally, relative air humidity can be increased up to 80 % or 95. The follow‐

Opto-Electronic Packaging http://dx.doi.org/10.5772/51626 439

Wheat heat at constant temperature Dry heat at cycling temperatures

**5.** DIN (Deutsche Industrie Norm, German Industrial Standard Organization) 40046

ing institutions have developed the commonly used testing standards:

Low pressure

Solar radiation

Packaging and manufacturing Welding, ultrasonic cleaning, mechanical strength of connector pins

A typical set-up used for temperature testing is depicted in figure 29. Further, the device un‐ der test (DUT) is placed into a humidity controlled environmental test chamber. The tem‐ perature behavior of the opto-electronic module is mostly characterized by measuring the variation of optical output power. A plot of a typical temperature test between +15°C and +40°C is shown in figure 30. The temperature behavior of a laser module shows a maximum output variation of ±0.15 dB with temperature which is a real good result. Three cycles with‐

**6.** MIL-STD (Military Standard/USA) 810/202

**8.** Telcordia 6R-78, -326, -357, -468

**Stress parameters Tests**

div. Sealing

**Table 4.** Environmental test parameters.

**Figure 29.** Environmental test set-up.

**7.** IEC (International Engineering Committee) 60068-X

Climate Cold, dry heat, dust and sand

Mechanical Dropping, acceleration, vibrations Chemical and biological Corrosive atmosphere, growths of mold

**Figure 27.** Arrayed waveguide grating module [19].
