HFBR-2464K Просмотр технического описания (PDF) - HP => Agilent Technologies

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HFBR-2464K

Low Cost, Miniature Fiber Optic Components with ST®, SMA, SC and FC Ports

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5 MBd Logic Link Design

If resistor R1 in Figure 2 is

70.4 Ω, a forward current IF of

48 mA is applied to the HFBR-

14X4 LED transmitter. With IF =

48 mA the HFBR-14X4/24X2

logic link is guaranteed to work

with 62.5/125 µm fiber optic

cable over the entire range of 0

to 1750 meters at a data rate of

dc to 5 MBd, with arbitrary data

format and pulse width distortion

typically less than 25%. By

setting R1 = 115 Ω, the transmit-

ter can be driven with IF = 30 mA,

if it is desired to economize on

power or achieve lower pulse

distortion.

The following example will illus-

trate the technique for selecting

the appropriate value of IF and R1.

Maximum distance required

= 400 meters. From Figure 3 the

drive current should be 15 mA.

From the transmitter data

VF = 1.5 V (max.) at IF = 15 mA

as shown in Figure 9.

R1

=

V–C–C––-–V–F–

IF

=

5––V––-–1–.–5–V–

15 mA

R1 = 233␣ Ω

The curves in Figures 3, 4, and 5

are constructed assuming no in-

line splice or any additional

system loss. Should the link

consists of any in-line splices,

these curves can still be used to

calculate link limits provided they

are shifted by the additional

system loss expressed in dB. For

example, Figure 3 indicates that

with 48 mA of transmitter drive

current, a 1.75 km link distance

is achievable with 62.5/125 µm

fiber which has a maximum

attenuation of 4 dB/km. With

2 dB of additional system loss, a

1.25 km link distance is still

achievable.

Figure 2. Typical Circuit Configuration.

56

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