ATTENUATORS

Variable Attenuators


Fotec Variable Attenuator with Connector Assemblies
AFS Variable Attenuator with Connector Assemblies

The Advanced Fiber Solutions variable attenuators are ideal for simulating cable loss for lab testing of link power margin or reducing power in links where receivers are being overloaded. Advanced Fiber Solutions variable attenuators are of the gap-loss type. The loss is induced by pulling the connector end-faces apart. Since the light exits in an expanding cone, the receiving fibre will capture less light as the gap gets larger.
Air gap attenuators are ideal for use with any LED systems and many laser systems. Some laser systems, especially high-speed digital links (over 1 GB/s) or analog CATV systems may not operate well with these attenuators due to back reflections. If you are using these attenuators in those types of systems, you should use the ATT-120 with a FC/APC connector, which have very low return loss even when unmated.
Advanced Fiber Solutions variable attenuators mate to cables with the connector type listed. If you need to use them with other connector types, use hybrid cables. With one connector matching the attenuator and the other connector mating to the network connector. The fibre type used should also match the network fibre type, with one exception: if in a single mode network your receiver uses a multimode "bucket" fibre, you can use a matching multimode fibre on the receiver side of the attenuator.

Attenuator Types
Connector Style Order Code dB loss range Application
ST ATT-110 ~1 to 35 dB MM or SM
FC ATT-120 ~1 to 35 dB MM or SM
SC ATT-130 ~1 to 35 dB MM or SM

Attaching Interface Cables
· For use, the attenuator is attached between two mating cables, replacing the usual splice bushing/adaptor. Refer to the instructions below appropriate to the attenuator you are using.

ATT-110 (ST) and ATT-130 (SC)
· Attach the input and the output cables directly to the female receptacles on the attenuator as you would normally with a splice bushing.

ATT-120 (FC)
· Unscrew the attenuator fully and remove the outer half of the attenuator body.
· Unscrew the connector interface adapter from the inner part of the attenuator using the tool supplied.
· Thread the cable through the attenuator body.
· Attach the interface adapter to the connector on the cable
· Reattach the adapter into the attenuator body using the tool supplied, insure the adapter is tightened snugly.
· Screw the outside of the attenuator body back on.
· Attach the input cable directly to the female receptacle on the other end of the attenuator

Setting the Attenuator Loss
The Advanced Fibre Solutions variable attenuators can be set to any loss value within the operating range desired using a fibre optic source and power meter, such as found in the Advanced Fiber Solutions test kits. You can set the loss either by measuring the actual loss, preferred for testing system margin in the lab, or by setting the receiver power level, when using them in an operating network.


Calibrating Actual Loss
 If you wish to calibrate the actual loss of the attenuator, you need to measure the optical power going into the attenuator and the optical power coming out, similar to testing the loss of a patch cord cable.


1. Attach input cable of fibre optic source.
2. Connect meter to input cable, measure power level in dB.
3. Attach attenuator with output cable to input cable.
4. Attach meter to end of output cable, measure power in dB after attenuation.
5. Calculate loss in dB by subtracting the two values.

Setting Receiver Power
1. Attach attenuator to receiver end of the network cable just before the receiver.
2. Connect the power meter to network cable and measure power with network source on.
3. Adjust attenuator to proper receiver power level and lock with screw.

Note: All AFS variable attenuators require fibre optic patch cables