ACS411CS Semtech Corporation, ACS411CS Datasheet - Page 24

• Manufacturer Part Number: ACS411CS
• Description: Acapella Optical Modem ic
• Manufacturer: Semtech Corporation

ACS411CS PRE-RELEASE Issue 6.0 July 1999.
The link budget is the difference between the power
coupled to the fiber via the transmit Laser/LED and
the power required to realise the minimum input-
amplifier current via the receive PIN/LED. The link
budget is normally specified in dB, and represents
the maximum attenuation allowed between
communicating Lasers/LEDs. The budget is utilised
in terms of the cable length, cable connectors and
splices. It usually includes an operating margin to
allow for degradation in LASER/LED performance.
The power coupled to the cable is a function of the
efficiency of the Laser/LED, the current applied to
the Laser/LED and the type of the fiber optic cable
employed.
Link Budgets
Twin Fiber LED link (880nm LED + PIN)
Link Budget Example (Rtset set so LED launch current = 100 mA peak)
Fiber type Glass (multimode)
Fiber size 62.5micron
Minimum transmit couple power to fiber (µW)
Minimum PIN responsivity (A/W)
Minimum ACS9020 sensitivity (nA)
Minimum input power to ACS9020 amplifier (µW)
Link budget (dB) (multi mode fiber attenuation = 3 dB/km)
Twin Fiber LASER link (1310nm Laser and PIN)
Link Budget Example (Rtset set so LASER launch current = 25 mA peak)
Fiber type Glass (single mode)
Fiber size 9 micron
Minimum transmit couple power to fiber (µW)
Minimum PIN responsivity (A/W)
Minimum ACS9020 sensitivity (nA)
Minimum input power to ACS9020 amplifier (µW)
Link budget (dB) (single mode fiber attenuation = 0.3 dB/km)
Single Fiber LASER link (1310nm and 1510nm WDM device)
Link Budget Example (Rtset set so LASER launch current = 25 mA peak)
Fiber type Glass (single mode)
Fiber size 9 micron
Minimum transmit couple power to fiber (µW)
Minimum PIN responsivity (A/W)
Minimum ACS9020 sensitivity (nA)
Minimum input power to ACS9020 amplifier (µW)
Link budget (dB) (single mode fiber attenuation = 0.3 dB/km)
Figure 14: Link bugdet examples.
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100
0.1
1500
20
1000
0.8
1500
4
27
1000
0.8
1500
4
27
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