Buyer’s guide

Fiber optic cannulas and ceramic ferrules

Choose the ferrule size, core size, numerical aperture and fiber length for each implant, then pick a patch cord and sleeve that fit it.

Know the parts and how they connect

A fiber optic cannula, also called an optical cannula or fiber implant, has two parts. A short optical fiber goes into the brain, and a ceramic ferrule holds its top end above the skull.

The patch cord ends in a ferrule too. A ceramic sleeve, also called a mating sleeve, slides over both ferrules and holds them end to end, so light passes from the cord’s fiber into the implant’s.

In photometry, fluorescence from a sensor such as GCaMP travels back along the same path to the detector.

Patch cordFerrule on the cordCeramic sleeveImplant ferruleSkullOptical fiberLight at the target
A patch cord joins the implant through a ceramic sleeve. Not to scale.

Choose 1.25 mm or 2.5 mm ferrules

Ferrules come in two common outer diameters, 1.25 mm and 2.5 mm. The smaller size is lighter and takes less room on the skull, which helps on a mouse or with two implants side by side.

The implant, the sleeve and the ferrule on the patch cord must all be the same size. Keeping to one ferrule size lets every cord plug into every implant in the lab.

If you already own patch cords or a photometry system, check their ferrule size before you order implants.

Ask the seller

  • Which ferrule sizes do the implants, sleeves and patch cords come in?
  • How long is the ferrule on each implant?
  • Will your sleeves fit the patch cords I already own?

Choose the core size and numerical aperture

The core is the center of the fiber that carries the light. Cores of 100, 200, 300 and 400 µm are common. A wider core lights a wider area, while a narrower core makes a thinner fiber that displaces less tissue.

The numerical aperture, or NA, sets the angle of the cone of light that leaves the tip. Light leaves a 0.22 NA fiber in a narrow cone and a 0.50 NA fiber in a wide one, and 0.39 NA falls between them.

Order patch cords with the same core size and NA as the implants. If the cord’s core or NA is larger than the implant’s, some light is lost going in. If it is smaller, some fluorescence is lost on the way back.

The optogenetics irradiance calculator, linked below, estimates how core size and NA change the irradiance at your target.

Ask the seller

  • Which core sizes and NAs do the implants come in?
  • Do the patch cords come in the same core size and NA?
  • Which connector is on the other end of the patch cord?
  • Which wavelengths does the fiber carry?

For photometry, choose low-autofluorescence fiber

Under blue light, some fiber gives off a faint glow of its own, called autofluorescence, which raises the background beneath a small signal. For photometry, ask for fiber made for low autofluorescence, in the implant and in the patch cord.

A higher NA takes in light over a wider angle, so a photometry implant with a higher NA collects more fluorescence from a sensor such as GCaMP.

Ask the seller

  • Is the implant fiber made for low autofluorescence?
  • Is the patch cord made for low autofluorescence too?

Choose the fiber length from the target depth

The fiber below the ferrule sets how deep the tip can reach. The ferrule stops at the skull, so the fiber must be at least as long as the depth from the skull surface at the implant site to where the tip should be. If your coordinates give depth from the brain surface, add the thickness of the skull.

A slightly longer fiber also works. The ferrule then stays a little above the skull, and the cement that fixes the implant fills the gap.

For an angled approach, the length along the track is longer than the vertical depth. Enter your target and angle in the stereotaxic trajectory planner, linked below, to get the insertion depth along the track.

Ask the seller

  • Which fiber lengths can you make, and in what steps?
  • Is the length measured from the bottom of the ferrule?
  • Can you make a length that is not on the list?

Place the implant and protect the connection

A ferrule holder clamps the implant to the stereotaxic arm, so you can lower the fiber to its target and keep it still while the cement hardens.

Between sessions, cap the implant and the patch cord ends to keep dust off the end faces. Dust or a scratch on an end face blocks light where the ferrules meet. Clean both ends before you connect.

Keep spare sleeves and caps on hand, because they are small and easy to lose. If you make or repair your own implants, a fiber stripper removes the fiber’s coating before the fiber goes into a ferrule.

Ask the seller

  • Does the ferrule holder fit my stereotaxic arm?
  • Is the price for one implant or a pack?
  • How many sleeves and caps come in a pack?

Common questions

What is a fiber optic cannula?
It is an implant that carries light to a brain site for optogenetics or fiber photometry. A short optical fiber is held in a ceramic ferrule, and a patch cord connects to the ferrule through a sleeve.
What is a ceramic ferrule for optical fiber?
It is a small ceramic tube that holds the end of a fiber straight and centered. Two ferrules held end to end in a sleeve line up their fibers, so light passes between them.
Should I choose 1.25 mm or 2.5 mm ferrules?
Either size works when the implant, sleeve and patch cord match, so start from the size your cords or system already use. The 1.25 mm size is smaller and lighter, which suits the small skull of a mouse.
What does a ferrule holder do?
It holds an implant’s ferrule on a stereotaxic arm during surgery. You lower the fiber to its coordinates, fix the implant with cement, then release the holder.
What is a mating sleeve?
It is the ceramic sleeve that joins a patch cord to an implant. Both ferrules slide into it from opposite ends, so it must match their size.
Can one implant serve both optogenetics and photometry?
Yes, if your system can stimulate and record at the same site. One fiber then carries stimulation light in and the sensor’s fluorescence back out. Keep the stimulation color away from the colors the sensor uses.

Our implants and the parts that fit them

Our fiber optic cannulas come in both ferrule sizes, with sleeves, caps and a holder to match. Before you order, ask us to confirm your fiber lengths and how many implants come in a pack.

  • Fiber optic cannulas

    The ferrule is 1.25 mm across and 6.4 mm long, or 2.5 mm across and 10.5 mm long, in white or black. Cores of 200, 300 and 400 µm come at 0.22 and 0.39 NA, and at 0.50 NA the cores are 200 and 400 µm. Black ferrules also come with a 100 µm core at 0.22 NA. Fiber lengths run from 2 to 20 mm in 0.5 mm steps, and the fiber is rated for light from 400 to 2200 nm.

    See the cannulas

  • Ceramic sleeves

    They fit 1.25 mm or 2.5 mm ferrules and come 20 to a pack. Their product page names them the Optogenetics Ceramic Cannula, but each one is a sleeve that joins a cord to an implant.

    See the sleeves

  • Protective caps

    They fit 1.25 mm or 2.5 mm ferrule ends and come 200 to a pack.

    See the caps

  • Ferrule holder

    It holds a 1.25 mm or 2.5 mm ferrule on an 8 mm rod, and it is made for the stereotaxic instruments we sell.

    See the holder

  • Patch cords and rotary joint

    Patch cords that end in a 1.25 mm or 2.5 mm ferrule are on the accessories page, with a rotary joint for animals that move freely.

    See the accessories

  • Get a quote for your implants

    Tell us your ferrule size, core, NA and fiber lengths, and we will quote the implants and the parts that fit them.

    Ask about your implants