Customer checked https://apps.juniper.net/hct/product/?prd=EX4400-48F which doesn't list 100 Mbps transceivers.

Customer needs to use 100 Mbps SFP for EX4400-48F platform.

The EX-SFP-1FE-LX transceiver (Part Number: 740-028307) is supported on the EX4400-48F platform, as confirmed on the following documentation:

 EX-SFP-1FE-LX (Part Number: 740-028307)

https://apps.juniper.net/hct/model/?component=EX-SFP-1FE-LX

Introduced Release: Junos OS 22.1R1

I am including the following output from a EX4400-48F device for reference:

root@switch> show chassis hardware

Hardware inventory:

Item       Version Part number Serial number   Description

Chassis                YK4328880031   EX4400-48F

Pseudo CB 0

Routing Engine 0     BUILTIN   BUILTIN      RE-EX4400-48F

 mmcsd0 19680 MB MMCHC        03220067     eMMC Disk

 usb0 (addr 0.1) XHCI root HUB 0   0x8086      uhub0

FPC 0      REV 06  650-114385  YK4328880031   EX4400-48F

 CPU           BUILTIN   BUILTIN      FPC CPU

 PIC 0     REV 06  BUILTIN   BUILTIN      36x 1G SFP, 12x 1G/10G SFP/SFP+

  Xcvr 1    REV 01  740-028307  845201092842238  SFP-100-LX

 EX-SFP-1FE-LX transceiver (Part Number: 740-028307) is displayed on "show chassis hardware" output as expected.

On the other hand, the following Official Documentation for the Supported Hardware does not list it (by mistake), but the EX-SFP-1FE-LX transceiver (Part Number: 740-028307) is supported and already confirmed as compatible SFP.

 EX4400-48F - List of hardware components supported on the product along with its introduced software releases.

https://apps.juniper.net/hct/product/?prd=EX4400-48F

If needed, also check the following KB for the reported bug PR1720074:

 EX4400-48F: Juniper SFP with no-negotiation enabled on that port doesn't bring the SFP up.

https://supportportal.juniper.net/s/article/EX4400-Juniper-SFP-with-no-negotiation-enabled-on-that-port-doesnt-bring-the-SFP-up?language=en_US