Common Types of Optical Filters for Optical Modules:Bandpass Filters (BPF) – Allow a specific wavelength band to pass while blocking
others. Used in DWDM/CWDM systems. Edge Filters (Longpass/Shortpass) – Transmit wavelengths above (longpass) or below (shortpass)
a cutoff. Used for pump/signal separation in EDFAs. Notch Filters (Bandstop) – Block a narrow band of wavelengths. Used for laser
protection or ASE suppression. Gain Flattening Filters (GFF) – Equalize gain across wavelengths in EDFAs or Raman
amplifiers. Thin-Film Filters (TFF) – High stability, low loss, widely used in transceivers
(e.g., 100G/400G modules). Arrayed Waveguide Gratings (AWG) – Multi-channel filtering for high-density wavelength routing. Key Specifications:Center Wavelength (CWL) – e.g., 1310 nm, 1550 nm, or specific ITU grid channels. Bandwidth (FWHM or 0.5 dB/3 dB width) – e.g., 0.4 nm for DWDM, 13.5 nm for CWDM. Insertion Loss (IL) – Typically < 1.0 dB. Ripple – ≤ 0.3 dB (in-band flatness). Isolation/Rejection – e.g., > 25 dB at adjacent channels. Return Loss (RL) – ≥ 45 dB. Thermal Stability – < 2 pm/°C for DWDM. Reliability – Telcordia GR-1221/1209 compliant.
Applications in Optical Modules:Transceivers (SFP, QSFP, OSFP) – WDM multiplexing/demultiplexing. Coherent Modules – Linewidth narrowing and sideband filtering. PON OLT/ONU – Upstream/downstream wavelength separation. Optical Amplifiers – Pump rejection, gain flattening, ASE filtering.
Stock vs. Custom Filters:Standard stock – OD4@200-1700nm&OD7@1553.33nm,T>90%@1536.61nm, AOI 0° - Standard stock – OD4@200-1700nm&OD7@1536.61nm,T>90%@1553.33nm, AOI 0°
Custom options – Non-standard center λ, ultra-steep edges,
temperature-compensated designs, smaller footprint (e.g., 10*10 mm).
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